Lisandra Martin

1,4,7-Triazacyclononane hemihydrate

Publisher: International Union of Crystallography (IUCr)

Date: 22-01-2005

DOI: 10.1107/S1600536805000814

The missing link in the series [L2MIII 2(μ-O)(μ-MeCO2)2]2+ (M = Ti, V, Cr, Mn, Fe). Synthesis, crystal structure and magnetism of [L 2CrIII 2(μ-O)(μ-MeCO2) 2][BPh4]2

Publisher: Royal Society of Chemistry (RSC)

Date: 1990

DOI: 10.1039/C39900001767

Voltammetric, Spectroscopic, and Microscopic Investigation of the Oxidation of Solid and Solution Phases of Tetrathiafulvalene (TTF) to (TTF)(2)MO4 (M=Mo, W)

Publisher: Wiley

Date: 15-08-2018

DOI: 10.1002/CELC.201700463

Macrobicyclic chromium(III) hexaamine complexes

Publisher: American Chemical Society (ACS)

Date: 1986

DOI: 10.1021/IC00223A033

QCM-D fingerprinting of membrane-active peptides

Publisher: Springer Science and Business Media LLC

Date: 16-12-2011

DOI: 10.1007/S00249-010-0652-5

Abstract: The increasing prevalence of antibiotic-resistant bacteria is becoming a public health crisis. Antimicrobial peptides (AMPs) are a promising solution, because bacterial resistance is less likely. Quartz crystal microbalance with dissipation monitoring (QCM-D) is a versatile and valuable technique for investigation of these peptides. This article looks at the different approaches to the interpretation of QCM-D data, showing how to extract the maximum information from the data. Five AMPs of erse charge, length and activity are used as case studies: caerin 1.1 wild-type, two caerin 1.1 mutants (Gly15Gly19-caerin 1.1 and Ala15Ala19-caerin 1.1), aurein 1.2 and oncocin. The interaction between the AMP and a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane is analysed inter alia using frequency-dissipation plots (∆f-∆D plots) to ascertain the mechanism of action of the AMP. The ∆f-∆D plot can then be used to provide a fingerprint for the AMP-membrane interaction. Building up a database of these fingerprints for all known AMPs will enable the relationship between AMP structure and membrane activity to be better understood, hopefully leading to the future development of antibiotics without bacterial resistance.

Voltammetric studies on the inter-relationship between the redox chemistry of TTF, TTF+center dot, TTF2+ and HTTF+ in acidic media

Publisher: Royal Society of Chemistry (RSC)

Date: 2015

DOI: 10.1039/C4RA16588H

Abstract: The chemistry of oxidized forms of TTF in acidified CH 3 CN has been established using electrochemical and spectroscopic techniques.

Single-Molecule Imaging of Amyloidβ Protein (Aβ) of Alzheimer's Disease. From Single-Molecule Structures to Aggregation Mechanisms and Membrane Interactions

Publisher: Elsevier

Date: 2013

DOI: 10.1016/B978-0-12-394431-3.00005-5

Polymer Nanodiscs and Their Bioanalytical Potential

Publisher: Wiley

Date: 30-07-2021

DOI: 10.1002/CHEM.202101572

Abstract: Membrane proteins (MPs) play a pivotal role in cellular function and are therefore predominant pharmaceutical targets. Although detailed understanding of MP structure and mechanistic activity is invaluable for rational drug design, challenges are associated with the purification and study of MPs. This review delves into the historical developments that became the prelude to currently available membrane mimetic technologies before shining a spotlight on polymer nanodiscs. These are soluble nanosized particles capable of encompassing MPs embedded in a phospholipid ring. The expanding range of reported hipathic polymer nanodisc materials is presented and discussed in terms of their tolerance to different solution conditions and their nanodisc properties. Finally, the analytical scope of polymer nanodiscs is considered in both the demonstration of basic nanodisc parameters as well as in the elucidation of structures, lipid–protein interactions, and the functional mechanisms of reconstituted membrane proteins. The final emphasis is given to the unique benefits and applications demonstrated for native nanodiscs accessed through a detergent free process.

Template syntheses of chiral tetradentate ligands derived from L-amino acids. Structural and spectroscopic characterization of the free ligands and of their copper(II) complexes

Publisher: Royal Society of Chemistry (RSC)

Date: 1991

DOI: 10.1039/DT9910000277

Helical intermediate formation and its role in amyloids of an amphibian antimicrobial peptide

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D3CP00104K

Abstract: The formation of helical intermediates and an increase in local concentration in peptide aggregates appear to be crucial in the amyloid formation of amyloidogenic hibian peptide uperin-3.5.

Subtle differences in initial membrane interactions underpin the selectivity of small antimicrobial peptides

Publisher: Wiley

Date: 22-12-2015

DOI: 10.1002/CPLU.201402318

Abstract: Host‐secreted antimicrobial peptides (AMPs) are found in virtually all organisms, often providing innate immunity as the first line of defence against pathogens. Many AMPs kill pathogens by disrupting their cellular membranes and thus are similar to some antibiotic drugs. Likely drug candidate AMPs are found in non‐mammalian hosts but are also haemolytic. Thus, it is crucial to understand the origins of membrane specificity and selectivity of the action of these AMPs. In this study, the membrane specificity of action of citropin 1.1, a 16‐residue AMP, was studied by using a quartz crystal microbalance on the basis of mass and viscoelasticity changes in comparison to aurein 1.2 (13 residues) and maculatin 1.1 (21 residues). The membrane selectivity was largely reflected in the nature of the initial interaction of the peptide with the membrane. This initial interaction might determine whether the peptide transforms into a membrane‐disrupting α‐helical conformation and highlights subtle differences in the repositioning of this α‐helical peptide in the membrane, as reflected by the viscoelasticity data, thus signifying the mechanistic pathway to membrane disruption.

Controlling protein orientation at interfaces using histidine tags: an alternative to Ni/NTA

Publisher: American Chemical Society (ACS)

Date: 02-2005

DOI: 10.1021/JA045084G

Abstract: A strategy for immobilizing histidine-tagged proteins at surfaces has been developed by using a macrocyclic chelator that enhances the stability and specificity of conventional histidine-tag technology and allows application of this technology to long-term studies including direct electrochemistry.

Relaxation processes in aromatic methyl groups. ii: Methyl-methyl nuclear overhauser enhancements

Publisher: CSIRO Publishing

Date: 1990

DOI: 10.1071/CH9900741

Abstract: A range of compounds with methyl groups disposed ortho and peri on heteroaromatic frameworks have been prepared, and T1 values and methyl-methyl Overhauser effects measured for them. Most of the n.O.e . Values were ≤6%, but two ex les of methyls flanked by two others exhibited values of 9% (6-hydroxy-4,4,5,7-tetramethyl-3,4-dihydro-2H-benzopyran-2-one) and 15% (1,4,5,8,9-pentamethylcarbazole).

Effects of guanidino modified aminoglycosides on mammalian membranes studied using a quartz crystal microbalance

Publisher: Royal Society of Chemistry (RSC)

Date: 2017

DOI: 10.1039/C7MD00054E

Abstract: Drug-delivery of aminoglycosides was studied using the biophysical platform of a quartz crystal microbalance. Guanidino modification enhanced the biomolecule-membrane interaction.

Synthetic precursors for TCNQF(4)(2-) compounds: synthesis, characterization, and electrochemical studies of (Pr4N)(2)TCNQF(4) and Li(2)TCNQF(4)

Publisher: American Chemical Society (ACS)

Date: 15-11-2012

DOI: 10.1021/JO301403V

Abstract: Careful control of the reaction stoichiometry and conditions enables the synthesis of both LiTCNQF(4) and Li(2)TCNQF(4) to be achieved. Reaction of LiI with TCNQF(4), in a 4:1 molar ratio, in boiling acetonitrile yields Li(2)TCNQF(4). However, deviation from this ratio or the reaction temperature gives either LiTCNQF(4) or a mixture of Li(2)TCNQF(4) and LiTCNQF(4). This is the first report of the large-scale chemical synthesis of Li(2)TCNQF(4). Attempts to prepare a single crystal of Li(2)TCNQF(4) have been unsuccessful, although air-stable (Pr(4)N)(2)TCNQF(4) was obtained by mixing Pr(4)NBr with Li(2)TCNQF(4) in aqueous solution. Pr(4)NTCNQF(4) was also obtained by reaction of LiTCNQF(4) with Pr(4)NBr in water. Li(2)TCNQF(4), (Pr(4)N)(2)TCNQF(4), and Pr(4)NTCNQF(4) have been characterized by UV-vis, FT-IR, Raman, and NMR spectroscopy, high resolution electrospray ionization mass spectrometry, and electrochemistry. The structures of single crystals of (Pr(4)N)(2)TCNQF(4) and Pr(4)NTCNQF(4) have been determined by X-ray crystallography. These TCNQF(4)(2-) salts will provide useful precursors for the synthesis of derivatives of the dianions.

Crystal structure of 2-thiophenealdoxime, C5H5NOS

Publisher: Walter de Gruyter GmbH

Date: 2000

DOI: 10.1515/NCRS-2000-0161

Optimization of oncocin for antibacterial activity using a SPOT synthesis approach: extending the pathogen spectrum to Staphylococcus aureus

Publisher: Springer Science and Business Media LLC

Date: 03-09-2015

DOI: 10.1007/S00726-015-2082-2

Abstract: The identification of lead molecules against multidrug-resistant bacteria ensuing the development of novel antimicrobial drugs is an urgent task. Proline-rich antimicrobial peptides are highly active in vitro and in vivo, but only against a few Gram-negative human pathogens, with rather weak activities against Pseudomonas aeruginosa and Staphylococcus aureus. This reduced level of efficacy could be related to inadequate uptake mechanisms or structural differences of the intracellular target proteins, i.e., the 70S ribosome or chaperone DnaK. Here we synthesized peptide arrays on cellulose membranes using cleavable linkers to release the free in idual peptides for further antimicrobial tests. Thus, a library of singly substituted oncocin analogs was produced by replacing each residue by all other 19 canonical amino acids yielding a set of 361 in idual peptides to be evaluated against a luminescent P. aeruginosa strain. Thirteen substitutions appeared promising and their improved antibacterial activities were confirmed for different bacteria after larger scale synthesis of these analogs. By combining two favorable substitutions into one peptide, we finally obtained an oncocin analog that was ten times more active against P. aeruginosa and even 100-fold more active against S. aureus than the original oncocin, providing minimal inhibitory concentrations of 4-8 and 0.5 µg/mL, respectively.

Assembly of streptolysin O pores assessed by quartz crystal microbalance and atomic force microscopy provides evidence for the formation of anchored but incomplete oligomers

Publisher: Elsevier BV

Date: 2015

DOI: 10.1016/J.BBAMEM.2014.10.012

Abstract: Streptolysin O (SLO) is a bacterial pore forming protein that is part of the cholesterol dependent cytolysin (CDC) family. We have used quartz crystal microbalance with dissipation monitoring (QCM-D) to examine SLO membrane binding and pore formation. In this system, SLO binds tightly to cholesterol-containing membranes, and assembles into partial and complete pores confirmed by atomic force microscopy. SLO binds to the lipid bilayer at a single rate consistent with the Langmuir isotherm model of adsorption. Changes in dissipation illustrate that SLO alters the viscoelastic properties of the bilayer during pore formation, but there is no loss of material from the bilayer as reported for small membrane-penetrating peptides. SLO mutants were used to further dissect the assembly and insertion processes by QCM-D. This shows the signature of SLO in QCM-D changes when pore formation is inhibited, and that bound and inserted SLO forms can be distinguished. Furthermore a pre-pore locked SLO mutant binds reversibly to lipid, suggesting that the partially complete wtSLO forms observed by AFM are anchored to the membrane.

Detailed electrochemical analysis of the redox chemistry of tetrafluorotetracyanoquinodimethane TCNQF(4), the radical anion [TCNQF(4)](center dot-), and the Dianion [TCNQF(4)](2-) in the presence of trifluoroacetic acid

Publisher: American Chemical Society (ACS)

Date: 29-07-2011

DOI: 10.1021/AC201373D

Abstract: The electrochemistry of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)), [TCNQF(4)](•-), and [TCNQF(4)](2-) have been studied in acetonitrile (0.1 M [Bu(4)N][ClO(4)]). Transient and steady-state voltammetric techniques have been utilized to monitor the generation of [TCNQF(4)](•-) and [TCNQF(4)](2-) anions as well as their reactions with trifluoroacetic acid (TFA). In the absence of TFA, the reduction of TCNQF(4) occurs via two, diffusion controlled, chemically and electrochemically reversible, one-electron processes where the reversible formal potentials are 0.31 and -0.22 V vs Ag/Ag(+). Unlike the TCNQ analogues, both [TCNQF(4)](•-) and [TCNQF(4)](2-) are persistent when generated via bulk electrolysis even under aerobic conditions. Voltammetric and UV-vis data revealed that although the parent TCNQF(4) does not react with TFA, the electrochemically generated radical anion and dianion undergo facile protonation to yield [HTCNQF(4)](•), [HTCNQF(4)](-) and H(2)TCNQF(4) respectively. The voltammetry can be simulated to give a complete thermodynamic and kinetic description of the complex, coupled redox and acid-base chemistry. The data indicate dramatically different equilibrium and rate constants for the protonation of [TCNQF(4)](•-) (K(eq) = 3.9 × 10(-6), k(f) = 1.0 × 10(-3) M(-1) s(-1)) and [TCNQF(4)](2-) (K(eq) = 3.0 × 10(3), k(f) = 1.0 × 10(10) M(-1) s(-1)) in the presence of TFA.

Spontaneous Redox Synthesis and Characterization of the Tetrathiafulvalene-Vanadium-Substituted Polyoxometalate Charge-Transfer Material TTF4 SVW11O40 : Comparison with the Mo Analogue

Publisher: American Chemical Society (ACS)

Date: 10-2014

DOI: 10.1021/IC501431C

Abstract: Both conventional solution-phase and direct solid-solid redox reactions between tetrathiafulvalene (TTF) and the vanadium-substituted polyoxometalate (n-Bu4N)3[SV(V)W11O40] give rise to microcrystalline or powdered semiconducting charge transfer solid material. A single-crystal X-ray structure derived from growing crystals from a MeCN-CH2Cl2 solution-phase redox reaction gives a stoichiometry of TTF4[SVW11O40]·2H2O·2CH2Cl2 and reveals that there are two crystallographically different TTF cation moieties based on (TTF2)(2+) dimers. While the color and morphology of the microcrystalline or powdered TTF4[SVW11O40] differ from the single crystals prepared for structural analysis, all materials are spectroscopically (infrared (IR), Raman with respect to the TTF bands, and electron paramagnetic resonance (EPR)) indistinguishable. Raman spectra suggest that the charge transfer is unevenly distributed across the (TTF2)(2+) dimers, which is postulated to give rise to enhanced mixed-valence features. Structural, spectral, and other properties, such as conductivity, are compared with results available on the recently published molybdenum TTF4[SVMo11O40]·2H2O·2CH2Cl2 analogue, where the charge distribution is uniform on all TTF cations. In both ex les, the position of the V atom is located over several sites. Elemental analysis and voltammetric data also are consistent with the formulations deduced from structural and spectroscopic studies. The conductivity at room temperature is in the semiconducting range, but significantly greater than that for the Mo analogue. EPR spectra at temperatures down to the liquid helium regime confirm the presence of paramagnetic V(IV) and paramagnetic oxidized TTF. The newly isolated TTF-SV(IV)W11O40 material also has magnetic functionality derived from the cationic and anionic components.

Structure and homogeneity of pseudo-physiological phospholipid bilayers and their deposition characteristics on carboxylic acid terminated self-assembled monolayers

Publisher: Elsevier BV

Date: 02-2009

DOI: 10.1016/J.BIOMATERIALS.2008.10.016

Abstract: Supported phospholipid bilayers are frequently used to establish a pseudo-physiological environment required for the study of protein function or the design of enzyme-based biosensors and biocatalytic reactors. These membranes are deposited from bilayer vesicles (liposomes) that rupture and fuse into a planar membrane upon adhesion to a surface. However, the morphology and homogeneity of the resulting layer is affected by the characteristics of the precursor liposome suspension and the substrate. Here we show that two distinct liposome populations contribute to membrane formation--equilibrium liposomes and small unilamellar vesicles. Liposome deposition onto carboxylic acid terminated self-assembled monolayers resulted in planar mono- and multilayer, vesicular and composite membranes, as a function of liposome size and composition. Quartz crystal microbalance data provided estimates for layer thicknesses and sheer moduli and were used for classification of the final structure. Finally, atomic force microscopy data illustrated the inherently inhomogeneous and dynamic nature of these membranes.

N-Terminal Ile-Orn- and Trp-Orn-Motif Repeats Enhance Membrane Interaction and Increase the Antimicrobial Activity of Apidaecins against Pseudomonas aeruginosa

Publisher: Frontiers Media SA

Date: 10-05-2016

DOI: 10.3389/FCELL.2016.00039

High resolution scanning tunnelling microscopy of the β-amyloid protein (Aβ1-40) of Alzheimer's disease suggests a novel mechanism of oligomer assembly

Publisher: Elsevier BV

Date: 07-2006

DOI: 10.1016/J.JSB.2006.02.013

Abstract: The aggregation of the beta-amyloid protein (Abeta) is an important step in the pathogenesis of Alzheimer's disease. There is increasing evidence that lower molecular weight oligomeric forms of Abeta may be the most toxic species in vivo. However, little is known about the structure of Abeta oligomers. In this study, scanning tunnelling microscopy (STM) was used to examine the structure of Abeta monomers, dimers and oligomers. Abeta1-40 was visualised by STM on a surface of atomically flat gold. At low concentrations (0.5 microM) small globular structures were observed. High resolution STM of these structures revealed them to be monomers of Abeta. The monomers measured approximately 3-4 nm in diameter. Internal structure was seen in many of the monomers consistent with a conformation in which the polypeptide chain is folded into 3 or 4 domains. Oligomers were seen after ageing the Abeta solution for 24 h. The oligomers were also 3-4 nm in width and appeared to be formed by the end-to-end association of monomers with the polypeptide chain oriented at 90 degrees to the axis of the oligomer. The results suggest that the oligomer formation can proceed through a mechanism involving the linear association of monomers.

Real-time examination of aminoglycoside activity towards bacterial mimetic membranes using Quartz Crystal Microbalance with Dissipation monitoring (QCM-D)

Publisher: Elsevier BV

Date: 02-2015

DOI: 10.1016/J.BBAMEM.2014.10.019

Abstract: The rapid increase in multi-drug resistant bacteria has resulted in previously discontinued treatments being revisited. Aminoglycosides are effective "old" antibacterial agents that fall within this category. Despite extensive usage and understanding of their intracellular targets, there is limited mechanistic knowledge regarding how aminoglycosides penetrate bacterial membranes. Thus, the activity of two well-known aminoglycosides, kanamycin A and neomycin B, towards a bacterial mimetic membrane (DMPC:DMPG (4:1)) was examined using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). The macroscopic effect of increasing the aminoglycoside concentration showed that kanamycin A exerts a threshold response, switching from binding to the membrane to disruption of the surface. Neomycin B, however, disrupted the membrane at all concentrations examined. At concentrations above the threshold value observed for kanamycin A, both aminoglycosides revealed similar mechanistic details. That is, they both inserted into the bacterial mimetic lipid bilayer, prior to disruption via loss of materials, presumably aminoglycoside-membrane composites. Depth profile analysis of this membrane interaction was achieved using the overtones of the quartz crystal sensor. The measured data is consistent with a two-stage process in which insertion of the aminoglycoside precedes the 'detergent-like' removal of membranes from the sensor. The results of this study contribute to the insight required for aminoglycosides to be reconsidered as active antimicrobial agents/co-agents by providing details of activity at the bacterial membrane. Kanamycin and neomycin still offer potential as antimicrobial therapeutics for the future and the QCM-D method illustrates great promise for screening new antibacterial or antiviral drug candidates.

Redox-induced solid-solid state transformation of tetrathiafulvalene (TTF) microcrystals into mixed-valence and pi-dimers in the presence of nitrate anions

Publisher: Springer Science and Business Media LLC

Date: 24-10-2014

DOI: 10.1007/S10008-014-2656-Z

Kinetic and thermodynamic interplay of cation ingress and egress at a TCNQ-modified electrode in contact with aqueous electrolyte mixtures containing Co(II) and Ni(II) cations

Publisher: Springer Science and Business Media LLC

Date: 16-04-2013

DOI: 10.1007/S10008-013-2061-Z

The Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) Technique Applied to the Study of Membrane-Active Peptides

Publisher: CSIRO Publishing

Date: 2018

DOI: 10.1071/CH18129

Stereoselective Coordination to Chiral Matrices. Cobalt(III). Chemistry of Simple Facially Coordinating Chiral Triamines

Publisher: Wiley

Date: 20-06-1990

DOI: 10.1002/HLCA.19900730413

A Homodimer Model Can Resolve the Conundrum as to How Cytochrome P450 Oxidoreductase and Cytochrome b5 Compete for the Same Binding Site on Cytochrome P450c17

Publisher: Bentham Science Publishers Ltd.

Date: 28-02-2017

DOI: 10.2174/1389203717666161220142957

Ammonium heptanitrosyltrithiotetraferrate monohydrate

Publisher: International Union of Crystallography (IUCr)

Date: 07-02-2004

DOI: 10.1107/S1600536804002338

Size Matters: A Mechanistic Model of Nanoparticle Curvature Effects on Amyloid Fibril Formation

Publisher: Cold Spring Harbor Laboratory

Date: 07-2021

DOI: 10.1101/2021.07.01.450782

Abstract: The aggregation of peptides into amyloid fibrils is linked to ageing-related diseases, such as Alzheimer’s disease and type 2 diabetes. Interfaces, particularly those with large nanostructured surface areas, can affect the kinetics of peptide aggregation, ranging from a complete inhibition to strong acceleration. While a number of physiochemical parameters determine interface effects, we here focus on the role of nanoparticle curvature for the aggregation of the amyloidogenic peptides Aβ 40 , NNFGAIL, GNNQQNY and VQIYVK. Nanoparticles (NPs) provided a surface for peptide monomers to adsorb, enabling the nucleation into oligomers and fibril formation. High surface curvature, however, destabilized prefibrillar structures, providing an explanation for inhibitory effects on fibril growth. Thioflavin T (ThT) fluorescence assays as well as dynamic light scattering (DLS), atomic force microscopy (AFM) and electron microscopy experiments revealed NP size-dependent effects on amyloid fibril formation, with differences between the peptides. While 5 nm gold NPs (AuNP-5) retarded or inhibited the aggregation of most peptides, larger 20 nm gold NPs (AuNP-20) tended to accelerate peptide aggregation. Molecular dynamics (MD) studies demonstrated that NPs’ ability to catalyze or inhibit oligomer formation was influenced by the oligomer stability at curved interfaces which was lower at more highly curved surfaces. Differences in the NP effects for the peptides resulted from the peptide properties (size, aggregation propensity) and concomitant surface binding affinities. The results can be applied to the design of future nanostructured materials for defined applications.

Membrane-Mediated Protein–Protein Interactions of Cholesterol Side-Chain Cleavage Cytochrome P450 with its Associated Electron Transport Proteins

Publisher: Wiley

Date: 22-07-2016

DOI: 10.1002/CPLU.201600272

Abstract: Cytochrome P450scc (P450scc or CYP11A1) catalyses the first enzymatic step of steroid biosynthesis, the cleavage of the side chain of cholesterol to produce pregnenolone in the mitochondrion. The activity of P450scc is dependent upon electron delivery from NADPH-dependent adrenodoxin reductase (AdR), via adrenodoxin (Adx), to the P450scc. However, despite the structural and kinetic data that supports the mechanism by which Adx shuttles electrons one at a time between AdR and the P450scc, there are limited data available on the influence of the lipid membrane on these essential interactions. In this paper, the protein-membrane interactions between P450scc and its redox partners were examined on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes containing cholesterol (20 %), using a quartz crystal microbalance with dissipation monitoring. P450scc showed strong binding to these membranes, whereas AdR and Adx both showed weaker association. If pre-mixed, all three proteins bound independently to the membrane layer in a distinctive two-stage process, as observed by frequency changes upon binding. Concomitant changes in the dissipation revealed specific protein-protein interaction occurs upon reaching a critical concentration of proteins in the membrane layer. These changes were specific for the binding of the three pre-mixed proteins and were not observed for a binary mixture of P450 and Adx, or sequential binding of the three proteins. A simple model was developed for the binding of all three proteins in a 1:1:1 mixture to the membrane and reproduces the experimental data describing the interaction of P450scc with the other proteins (AdR and Adx) after initial binding of the in idual proteins. Thus, we conclude that the lipid membrane assists in the assembly of electron transport proteins and the activity of P450scc by providing a surface for the localised concentration of proteins, enabling them to act together as a metabolon.

Voltammetric study of proton-gated electron transfer in a mutant ferredoxin. Altering aspartate to asparagine blocks oxidation of the [3Fe-4S] cluster of Azotobacter vinelandii ferredoxin I

Publisher: American Chemical Society (ACS)

Date: 12-1993

DOI: 10.1021/JA00079A049

Electrochemical and Chemical Synthesis of [ZnTCNQF4(DMF)2]·2DMF - A 2D Network Coordination Polymer

Publisher: Wiley

Date: 05-06-2019

DOI: 10.1002/EJIC.201900431

Probing the stability of the disulfide radical intermediate of thioredoxin using direct electrochemistry

Publisher: Springer Science and Business Media LLC

Date: 11-2003

DOI: 10.1007/S10989-004-2410-Y

Lipid Oxidation Controls Peptide Self-Assembly near Membranes

Publisher: Cold Spring Harbor Laboratory

Date: 03-08-2022

DOI: 10.1101/2022.08.02.502408

Abstract: The self-assembly of peptides into supramolecular fibril structures has been linked to neurodegenerative diseases such as Alzheimer’s disease but has also been observed in functional roles. Peptides are physiologically exposed to crowded environments of biomacromolecules, and particularly membrane lipids, within a cellular milieu. Previous research has shown that membranes can both accelerate and inhibit peptide self-assembly. Here, we studied the impact of biomimetic membranes that mimic cellular oxidative stress and compared this to mammalian and bacterial membranes. Using molecular dynamics simulations and experiments, we propose a model that explains how changes in peptide-membrane binding, electrostatics, and peptide secondary structure stabilization determine the nature of peptide self-assembly. We explored the influence of zwitterionic (POPC), anionic (POPG) and oxidized (PazePC) phospholipids, as well as cholesterol, and mixtures thereof, on the self-assembly kinetics of the amyloid β (1–40) peptide (Aβ 40 ), linked to Alzheimer’s disease, and the amyloid-forming antimicrobial peptide uperin 3.5 (U3.5). We show that the presence of an oxidized lipid had similar effects on peptide self-assembly as the bacterial mimetic membrane. While Aβ 40 fibril formation was accelerated, U3.5 aggregation was inhibited by the same lipids at the same peptide-to-lipid ratio. We attribute these findings and peptide-specific effects to differences in peptide-membrane adsorption with U3.5 being more strongly bound to the membrane surface and stabilized in an α-helical conformation compared to Aβ 40 . Different peptide-to-lipid ratios resulted in different effects. Molecular dynamics simulations provided detailed mechanistic insights into the peptide-lipid interactions and secondary structure stability. We found that electrostatic interactions are a primary driving force for peptide-membrane interaction, enabling us to propose a model for predictions how cellular changes might impact peptide self-assembly in vivo , and potentially impact related diseases.

Celebrating Professor Alan Bond’s 70th Birthday

Publisher: CSIRO Publishing

Date: 2017

DOI: 10.1071/CHV70N9_FO

Exploring the Role of Peptide Helical Stability in the Propensity of Uperin 3.x Peptides toward Beta-Aggregation

Publisher: American Chemical Society (ACS)

Date: 15-12-2020

DOI: 10.1021/ACS.JPCB.0C10000

Novel Engineered Ion Channel Provides Controllable Ion Permeability for Polyelectrolyte Microcapsules Coated with a Lipid Membrane

Publisher: Wiley

Date: 08-01-2009

DOI: 10.1002/ADFM.200800483

Super‐Efficient Platinum Catalyst Derived from a Semiconducting, DMF Solvate: Structural, Spectroscopic, Electrochemical, and Catalytic Characterization

Publisher: Wiley

Date: 26-06-2014

DOI: 10.1002/CCTC.201402134

Amyloid aggregation and membrane activity of the antimicrobial peptide uperin 3.5

Publisher: Wiley

Date: 23-02-2018

DOI: 10.1002/PEP2.24052

AFM study of morphological changes associated with electrochemical solid-solid transformation of three-dimensional crystals of TCNQ to metal derivatives (metal∈=∈Cu, Co, Ni; TCNQ∈= ∈tetracyanoquinodimethane)

Publisher: Springer Science and Business Media LLC

Date: 27-09-2008

DOI: 10.1007/S10008-007-0423-0

Specific and selective peptide-membrane interactions revealed using quartz crystal microbalance

Publisher: Elsevier BV

Date: 12-2007

DOI: 10.1529/BIOPHYSJ.107.116525

Crystal structure of bis(1,4-dimethyl-1,4,7-triazacyclononyl)-μ-chloro-μ-hydroxodicopper(II) perchlorate, C16H39ClCu2N6O(ClO4) 2

Publisher: Walter de Gruyter GmbH

Date: 03-1999

DOI: 10.1515/NCRS-1999-0123

Systematic Approach to the Synthesis of Cobaltocenium Salts with Reduced Forms of TCNQF4: Two [Cp2Co](TCNQF4) Polymorphs and [Cp2Co]Li(TCNQF4)

Publisher: American Chemical Society (ACS)

Date: 15-04-2019

DOI: 10.1021/ACS.CGD.8B01841

1-Undecyl-4,7-diaza-1-azoniatricyclo[5.2.1.0^4,10]decane iodide

Publisher: International Union of Crystallography (IUCr)

Date: 25-08-2006

DOI: 10.1107/S1600536806033095

Aquabis(4-morpholinyldithiocarbamato)-iron(III) trifluoromethanesulfonate

Publisher: International Union of Crystallography (IUCr)

Date: 31-10-2003

DOI: 10.1107/S1600536803024462

Electrochemically Directed Synthesis of Co2+ and Ni2+ Complexes with TCNQF(4)(2-) (TCNQF(4)=2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

Publisher: Wiley

Date: 25-09-2012

DOI: 10.1002/EJIC.201200774

Electrochemistry of TCNQF2 in acetonitrile in the presence of [Cu(CH3CN)4]+: Electrocrystallisation and characterisation of CuTCNQF2

Publisher: Elsevier BV

Date: 08-2018

DOI: 10.1016/J.ICA.2018.04.010

Synthesis of Ag and Au nanostructures in an ionic liquid: Thermodynamic and kinetic effects underlying nanoparticle, cluster and nanowire formation

Publisher: Royal Society of Chemistry (RSC)

Date: 2007

DOI: 10.1039/B618036A

Biomolecules Come Alive: A Computer-Based Laboratory Experiment for Chemistry Students

Publisher: American Chemical Society (ACS)

Date: 16-10-2018

DOI: 10.1021/ACS.JCHEMED.7B00931

Probing Electron Transfer in the Manganese-Oxide-Forming MnxEFG Protein Complex using Fourier Transformed AC Voltammetry: Understanding the Oxidative Priming Effect

Publisher: Wiley

Date: 10-08-2018

DOI: 10.1002/CELC.201700563

Real-Time Quartz Crystal Microbalance Monitoring of Free Docosahexaenoic Acid Interactions with Supported Lipid Bilayers

Publisher: American Chemical Society (ACS)

Date: 11-2016

DOI: 10.1021/ACS.LANGMUIR.6B01984

Abstract: Docosahexaenoic acid (DHA) is the most abundant polyunsaturated omega-3 fatty acid found in mammalian neuronal cell membranes. Although DHA is known to be important for neuronal cell survival, little is know about how DHA interacts with phospholipid bilayers. This study presents a detailed quartz crystal microbalance with dissipation monitoring (QCM-D) analysis of free DHA interactions with in idual and mixed phospholipid supported lipid bilayers (SLB). DHA incorporation and subsequent changes to the SLBs viscoelastic properties were observed to be concentration-dependent, influenced by the phospholipid species, the headgroup charge, and the presence or absence of calcium ions. It was observed that 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) SLBs incorporated the greatest amount of DHA concentration, whereas the presence of phospholipids, phosphatidylserine (PS), and phosphatidylinositol (PI) in a POPC SLB significantly reduced DHA incorporation and changed the SLBs physicochemical properties. These observations are hypothesized to be due to a substitution event occurring between DHA and phospholipid species. PS domain formation in POPC/PS 8:2 SLBs was observed in the presence of calcium ions, which favored DHA incorporation to a similar level as for a POPC only SLB. The changes in SLB thickness observed with different DHA concentrations are also presented. This work contributes to an understanding of the physical changes induced in a lipid bilayer as a consequence of its exposure to different DHA concentrations (from 50 to 200 μM). The capacity of DHA to influence the physical properties of SLBs indicates the potential for dietary DHA supplementation to cause changes in cellular membranes in vivo, with subsequent physiological consequences for cell function.

Reducing ZnO nanoparticle cytotoxicity by surface modification

Publisher: Royal Society of Chemistry (RSC)

Date: 2014

DOI: 10.1039/C4NR00458B

Abstract: ZnO surface properties control cytotoxicity by regulating nanoparticle uptake rather than by altering either intracellular or extracellular Zn dissolution rates.

Leone Spiccia Memorial Issue

Publisher: Wiley

Date: 25-06-2018

DOI: 10.1002/CPLU.201800262

Abstract: Leone Spiccia will be remembered as an outstanding scientist with a warm and generous personality. At the time of his death he was at the pinnacle of his scientific career with much more yet to be achieved. However, his legacy will continue to inspire new exciting science. Leone's scientific research was truly multidisciplinary and his friends and colleagues honour his memory with this special issue.

Analysis of perforin assembly by quartz crystal microbalance reveals a role for cholesterol and calcium-independent membrane binding

Publisher: Elsevier BV

Date: 12-2015

DOI: 10.1074/JBC.M115.683078

Crystalline ruthenium polypyridine nanoparticles: a targeted treatment of bacterial infection with multifunctional antibacterial, adhesion and surface-anchoring photosensitizer properties

Publisher: Royal Society of Chemistry (RSC)

Date: 2021

DOI: 10.1039/D1TB00103E

Abstract: Sph-Ru-MMT@PZ adheres to cell surfaces via sticky montmorillonite. Irradiation therapy generates reactive oxygen species that lyse E. coli , emitting an intense red fluorescence giving rapid feedback on the efficacy of antibacterial treatments.

Magnetism and Electronic Structure of a Series of Encapsulated First-Row Transition Metals

Publisher: American Chemical Society (ACS)

Date: 04-1990

DOI: 10.1021/IC00332A021

Oxidation of Thiosulphate using TCNQFn (n=0, 2, 4) Derivatives with a Tuneable Driving Force: Electrochemical and Spectrophotometric Detection of a Protonated Intermediate

Publisher: Wiley

Date: 20-08-2022

DOI: 10.1002/CELC.202200538

Abstract: Fluorine substituent effects associated with the and (n=0, 2, 4, TCNQ=7,7,8,8‐tetracyanoquinodimethane) half‐cell reactions provide access to a wide driving force range (∼850 mV) which is available to tune redox reactions in this case the oxidation of to by or . The ‐ / redox chemistry was studied by steady‐state and transient cyclic voltammetry and UV‐visible spectrophotometry in acetonitrile containing 5 % water and as the supporting electrolyte. In this mixed solvent system, all the (n=0, 2, 4)‐ / reactions were thermodynamically favourable, as were those of (n=2, 4). However, does not oxidize . These findings lead to a prediction that the reversible potential for the / half‐cell reaction lies between −0.083 and −0.278 V vs SHE. Interestingly, in the investigation of the reaction of and in a 1 : 2 concentration ratio, a protonated intermediate was detected. In contrast, when the oxidant was (2,5‐difluoro‐7,7,8,8‐tetracyanoquinodimethane) or (2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquino‐dimethane), no evidence for an analogous protonated intermediate was found. However, if equimolar ratios of (n=0, 2, 4) and were used, the intermediate was again detected. The structure of the intermediate, described as for convenience, is unknown, but this derivative of the redox chemistry is kinetically very stable and only very slowly deprotonated to or reduced by excess to give oxidized and deprotonated . Mechanisms are provided to explain the formation of the protonated intermediate.

Electrochemistry of cytochrome P450 17 alpha-hydroxylase/17,20-lyase (P450c17)

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.MCE.2016.09.034

Abstract: Within the superfamily of cytochrome P450 enzymes (P450s), there is a small class which is functionally employed for steroid biosynthesis. The enzymes in this class appear to have a small active site to accommodate the steroid substrates specifically and snuggly, prior to the redox transformation or hydroxylation to form a product. Cytochrome P450c17 is one of these and is also a multi-functional P450, with two activities, the first 17α-hydroxylation of pregnenolone is followed by a subsequent 17,20-lyase transformation to dehydroepiandrosterone (DHEA) as the dominant pathways to cortisol precursors or androgens in humans, respectively. How P450c17 regulates these two redox reactions is of special interest. There is a paucity of direct electrochemical studies on steroidogenic P450s, and in this mini-review we provide an overview of these studies with P450c17. Historical consideration as to the difficulties in obtaining reliable electrochemistry due to issues of handling proteins on an electrode, together with advances in the electrochemical techniques are addressed. Recent work using Fourier transformed alternating current voltammetry is highlighted as this technique can provide both catalytic information simultaneously with the underlying redox transfer with the P450 haem.

Biochemical and biophysical characterization of a novel plant protein disulfide isomerase.

Publisher: Wiley

Date: 04-11-2009

DOI: 10.1002/BIP.21113

Abstract: We recently isolated a protein disulfide isomerase (PDI) from the Rubiaceae (coffee family) plant Oldenlandia affinis (OaPDI) and demonstrated that it facilitates the production of disulfide-knotted defense proteins called cyclotides. PDIs are major folding catalysts in the eukaryotic ER where they are responsible for formation, breakage, or shuffling of disulfide bonds in substrate polypeptides and are important chaperones in the secretory pathway. Here, we report the first detailed analysis of the oligomerization behavior of a plant PDI, based on characterization of OaPDI using various biochemical and biophysical techniques, including size-exclusion chromatography, NMR spectroscopy, surface plasmon resonance and atomic force microscopy. In solution at low concentration OaPDI comprises mainly monomers, but fractions of dimers and/or higher-order oligomers were observed at increased conditions, raising the possibility that dimerization and/or oligomerization could be a mechanism to adapt to the various-sized polypeptide substrates of PDI. Unlike mammalian PDIs, oligomerization of the plant PDI is not driven by the formation of intermolecular disulfide bonds, but by noncovalent interactions. The information derived in this study advances our understanding of the oligomerization behavior of OaPDI in particular but is potentially of broader interest for understanding the mechanism and role of oligomerization, and hence the catalytic and physiological mechanism, of the ubiquitous folding catalyst PDI.

α7‐Nicotinic acetylcholine receptors mediate an Aβ₁₋₄₂‐induced increase in the level of acetylcholinesterase in primary cortical neurones

Publisher: Wiley

Date: 11-02-2004

DOI: 10.1046/J.1471-4159.2003.02296.X

Abstract: The beta-amyloid protein (Abeta) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non-cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Abeta have suggested that this increase may be due to a direct action of Abeta on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Abeta increases levels of AChE in primary cortical neurones. Abeta1-42 was more potent than Abeta1-40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Abeta peptides. The effect of Abeta1-42 on AChE was blocked by inhibitors of alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) as well as by inhibitors of L- or N-type voltage-dependent calcium channels (VDCCs), whereas agonists of alpha7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Abeta1-42 on AChE is due to an agonist effect of Abeta1-42 on the alpha7 nAChR.

Two-Step Electrochemically Directed Synthesis of Pr4N(TCNQ)(n) (n=1, 2): Preparation, Structure, and Properties of a Magnetically Isolated Dimer and a Quasi-One-Dimensional Chain

Publisher: Wiley

Date: 05-07-2011

DOI: 10.1002/CHEM.201100054

Abstract: Solid-state electrochemistry of a tetracyanoquinodimethane (TCNQ)-modified electrode in contact with a tetrapropylammonium cation (Pr(4)N(+)) electrolyte showed two electron-transfer steps to give Pr(4)N(TCNQ)(2) (1) and Pr(4)N(TCNQ) (2) rather than the traditional one-electron step to directly give Pr(4)N(TCNQ). Two thermodynamically stable Pr(4)N(+)-TCNQ stoichiometries, 1 and 2, were synthesized and characterized. The degree of charge transfer (ρ) calculated from the crystal structure is -0.5 for the TCNQ moieties in 1 and -1.0 for those in 2. Raman spectra for Pr(4)N(TCNQ)(2) show only one resonance for the extracyclic C=C stretching at 1423 cm(-1), which lies approximately midway between that of TCNQ at 1454 cm(-1) and TCNQ(-) at 1380 cm(-1). Both the magnetic susceptibility and EPR spectra are temperature-dependent, with a magnetic moment close to that for one unpaired electron per (TCNQ)(2) unit in 1, whereas 2 is almost diamagnetic. Pressed discs of both complexes show conductivity (1-2×10(-5) S cm(-1)) in the semiconductor range. For 1, the position of zero current for the steady-state voltammograms implies 50% of TCNQ(-) and 50% TCNQ(0) is present in solution, thereby supporting a dissociation of (TCNQ)(2)(-) in solution, but is indicative of only TCNQ(-) being present for 2.

A Tribute to Alan Bond on his 70th Birthday: 50 Years of Electrochemistry

Publisher: Wiley

Date: 28-02-2018

DOI: 10.1002/CELC.201800133

Electrochemical behaviour of human adrenodoxin on a pyrolytic graphite electrode

Publisher: Elsevier BV

Date: 04-2003

DOI: 10.1016/S1567-5394(02)00188-3

Abstract: Adrenodoxin (Adx) functions as a redox protein in the delivery of electrons to all mitochondrial cytochromes P450. In order to further characterize the human form of this protein, direct electrochemistry of human adrenodoxin (Hadx) has been observed for the first time on a pyrolytic graphite electrode (PGE) modified with poly-L-lysine. A single well-defined redox wave was observed with a midpoint potential of -448+/-3 mV vs. Ag/AgCl (sat. KCl) at scan rates of 10 mV/s and over the pH range 4.0-8.0. At slow scan rates, the reduction process was close to being electrochemically reversible whereas, at faster scan rates, only quasi-reversibility was observed. A correlation was observed between the peak separation (DeltaE) for the cyclic voltammograms and pH over a wide range of scan rates. The variation of DeltaE with pH was at a minimum (optimum reversibility) at pH 7.0 for all scan rates tested. This correlation may suggest that the direct electrochemistry method could possibly provide a means for determining protein or enzyme activity. The electron transfer rate constant, k(s), was determined to be 0.28 s(-1) at pH 7.0 and a small pH dependence was observed. The results obtained in this study demonstrate the facile nature of direct electron transfer for human adrenodoxin, and provide an estimate of the midpoint reduction potential at a pyrolytic graphite electrode via electrostatic immobilisation.

Novel Semiconducting Biomaterials Derived from a Proline Ester and Tetracyanoquinodimethane Identified by Handpicked Selection of Individual Crystals

Publisher: CSIRO Publishing

Date: 2012

DOI: 10.1071/CH12183

Abstract: Complex mixtures of cation : anion stoichometries often result from the syntheses of tetracyanoquinodimethane (TCNQ) salts, and often these cannot be easily separated. In this study, the reaction of N,N-dimethyl-d-proline-methylester (Pro(CH3)3+) with LiTCNQ resulted in a mixture of crystals. Hand selection and characterisation of each crystal type by X-ray, infrared, Raman and electrochemistry has provided two stoichometries, 1 : 1 [Pro(CH3)3TCNQ] and 2 : 3 ([(Pro(CH3)3)2(TCNQ)3]). A detailed comparison of these structures is provided. The electrochemical method provides an exceptionally sensitive method of distinguishing differences in stoichiometry. The room temperature conductivity of the mixture is 3.1 × 10–2 S cm–1, which lies in the semiconducting range.

Synthesis and structural characterization of a TCNQ based organic semi-conducting material with a 2:5 stoichiometry

Publisher: American Chemical Society (ACS)

Date: 22-11-2011

DOI: 10.1021/JO2018334

Abstract: The tetrabutylammonium complex with a 2:5 stoichiometry, (n-Bu(4)N)(2)(TCNQ)(5), has been prepared and structurally characterized by X-ray crystallography. Diagnostic bands in the Raman spectrum and signature features in the electrochemistry confirm that the TCNQ moieties are partially charged in the solid state. EPR, magnetic susceptibility, and electrical conductivity measurements are all consistent with (n-Bu(4)N)(2)(TCNQ)(5) behaving as a quasi-one-dimensional organic semiconductor.

The role of the coordination defect (CD) in the structures of anion-deficient, fluorite-related compounds

Publisher: International Union of Crystallography (IUCr)

Date: 19-01-2013

DOI: 10.1107/S205251921205110X

β‐Amyloid fibril formation is promoted by step edges of highly oriented pyrolytic graphite

Publisher: Wiley

Date: 2006

DOI: 10.1002/BIP.20549

Abstract: The aggregation of the amyloid-beta-protein (Abeta) is an important step in the pathogenesis of Alzheimer's disease. As Abeta fibrils are not found in all brain regions, endogenous factors may influence Abeta fibril formation. In this study, atomic force microscopy was used to investigate the role of surface phenomena in directing amyloid aggregation. Abeta1-40 was applied to a surface of highly oriented pyrolytic graphite at a concentration of 0.5 microM. Steps formed by edge-plane surface defects on the graphite were found to act as a template to promote the assembly of Abeta into fibrils. Initially, after being deposited on the graphite surface, Abeta had a uniform beaded morphology. However, after incubating (aging) the Abeta on the surface for several hours, the Abeta assembled along step edges to form linear aggregates. After more prolonged incubation, the linear Abeta aggregates fused to form mature fibrils with a distinctive helical morphology. The results demonstrate that surface interactions can promote the aggregation of Abeta into amyloid fibrils and they suggest that similar interactions could promote amyloid aggregation in vivo.

Investigation of the Redox and Acid-Base properties of TCNQF and TCNQF2: Electrochemistry, Vibrational Spectroscopy, and Substituent Effects

Publisher: Wiley

Date: 09-03-2018

DOI: 10.1002/CELC.201701387

2-[bis(1-methyl-2-benzimidazolylmethyl)-amino]ethanolchlorocopper(II) chloride hydrate

Publisher: International Union of Crystallography (IUCr)

Date: 15-06-1996

DOI: 10.1107/S0108270196001205

Electrochemically Directed Synthesis of Cobalt(II) and Nickel(II) TCNQF21–/2– Coordination Polymers: Solubility and Substituent Effects in the TCNQFn (n=0, 1, 2, 4) Series of Complexes

Publisher: CSIRO Publishing

Date: 2020

DOI: 10.1071/CH20187

Abstract: The reversible diffusion controlled cyclic voltammetry for the reduction of TCNQF­n0/1–/2– (where n=0, 1, 2, 4) changes significantly on addition of Co2+ and Ni2+ transition metal ions (M2+) because the kinetics associated with electrocrystallisation of the resulting coordination polymers [M(TCNQF2)2(H2O)2] and [M(TCNQF2)] are rapid on the voltammetric time scale. The voltammetry of solutions containing M2+ and TCNQF­2 was undertaken in acetonitrile (0.1M Bu4NPF6) at both GC and ITO electrodes. New one electron reduced TCNQF2 materials prepared via electrochemically directed synthesis were shown to have the formula [M(TCNQF2)2(H2O)2], assessed by vibrational (IR and Raman) spectroscopy, elemental analysis and thermogravimetric analysis. The solubility of [Ni(TCNQF2)2(H2O)2] (Ksp=8.29×10−11 M3) was significantly higher than the [Co(TCNQF2)2(H2O)2] (Ksp=1.43×10−11M3). Cyclic voltammetric data suggest the electrocrystallisation of two phases of [Ni(TCNQF2)2(H2O)2] occurs, which is not evident for [Co(TCNQF2)2(H2O)2]. Electrocrystallisation of the highly insoluble [M(TCNQF2)] was achieved at low M2+ and TCNQF2 concentrations. A comparison with published data on the voltammetry of TCNQF­n (n=0, 1, 2 and 4) for the series of TCNQF­n (n=0, 1, 2 and 4) containing M2+ is provided. An assessment of the electronic impact of the fluorine substituent of the underlying redox reactions also is established. Predictions are made for the voltammetric behaviour expected for the other transition metal cations with reduced TCNQFn derivatives.

Electrochemical Synthesis and Characterization of Semiconducting Ni(TCNQF4)2(H2O)2 (TCNQF4=2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

Publisher: Wiley

Date: 20-04-2012

DOI: 10.1002/EJIC.201101420

Redox and acid-base chemistry of 7,7,8,8-tetracyanoquinodimethane, 7,7,8,8-tetracyanoquinodimethane radical anion, 7,7,8,8-tetracyanoquinodimethane dianion, and dihydro-7,7,8,8-tetracyanoquinodimethane in acetonitrile

Publisher: American Chemical Society (ACS)

Date: 22-02-2012

DOI: 10.1021/AC2030514

Abstract: The chemistry and electrochemistry of TCNQ (7,7,8,8-tetracyanoquinodimethane), TCNQ(•-), TCNQ(2-), and H(2)TCNQ in acetonitrile (0.1 M Bu(4)NPF(6)) solution containing trifluoroacetic acid (TFA) has been studied by transient and steady-state voltammetric methods with the interrelationship between the redox and the acid-base chemistry being supported by simulations of the cyclic voltammograms. In the absence of acid, TCNQ and its anions undergo two electrochemically and chemically reversible one-electron processes. However, in the presence of TFA, the voltammetry is considerably more complex. The TCNQ(2-) dianion is protonated to form HTCNQ(-), which is oxidized to HTCNQ(•), and H(2)TCNQ which is electroinactive over the potential range of -1.0 to +1.0 V versus Ag/Ag(+). The monoreduced TCNQ(•-) radical anion is weakly protonated to give HTCNQ(•), which disproportionates to TCNQ and H(2)TCNQ. In acetonitrile, H(2)TCNQ deprotonates slowly, whereas in N,N-dimethylformamide or tetrahydrofuran, rapid deprotonation occurs to yield HTCNQ(-) as the major species. H(2)TCNQ is fully deprotonated to the TCNQ(2-) dianion in the presence of an excess concentration of the weak base, CH(3)COOLi. Differences in the redox and acid-base chemistry relative to the fluorinated derivative TCNQF(4) are discussed in terms of structural and electronic factors.

Enantiomeric selectivity of ruthenium (II) chiral complexes with antitumor activity, in vitro and in vivo.

Publisher: Elsevier BV

Date: 03-2020

DOI: 10.1016/J.JINORGBIO.2020.111339

Blood brain barrier-targeted delivery of double selenium nanospheres ameliorates neural ferroptosis in Alzheimer's disease

Publisher: Elsevier BV

Date: 11-2023

DOI: 10.1016/J.BIOMATERIALS.2023.122359

Mechanistic Scrutiny Identifies a Kinetic Role for Cytochrome b5 Regulation of Human Cytochrome P450c17 (CYP17A1, P450 17A1)

Publisher: Public Library of Science (PLoS)

Date: 20-11-2015

DOI: 10.1371/JOURNAL.PONE.0141252

μ-acetato-μ-aqua-μ-hydroxo-bis[(1,4-dimethyl-1,4,7- triazacyclononane-κ3N)-copper(II)] diperchlorate

Publisher: International Union of Crystallography (IUCr)

Date: 15-09-1998

DOI: 10.1107/S0108270198004375

Adsorption of Amyloidogenic Peptides to Functionalized Surfaces Is Biased by Charge and Hydrophilicity

Publisher: American Chemical Society (ACS)

Date: 19-09-2019

DOI: 10.1021/ACS.LANGMUIR.9B02063

Abstract: Surfaces are abundant in living systems, such as in the form of cellular membranes, and govern many biological processes. In this study, the adsorption of the amyloidogenic model peptides GNNQQNY, NNFGAIL, and VQIVYK as well as the amyloid-forming antimicrobial peptide uperin 3.5 (U3.5) were studied at low concentrations (100 μM) to different surfaces. The technique of a quartz crystal microbalance with dissipation monitoring (QCM-D) was applied as it enables the monitoring of mass binding to sensors at nanogram sensitivity. Gold-coated quartz sensors were used as unmodified gold surfaces or functionalized with self-assembled monolayers (SAMs) of alkanethiols (terminated as methyl, amino, carboxyl, and hydroxyl) resulting in different adsorption affinities of the peptides. Our objective was to evaluate the underlying role of the nature and feature of interfaces in biological systems which could concentrate peptides and impact or trigger peptide aggregation processes. In overall, the largely hydrophobic peptides adsorbed with preference to hydrophobic or countercharged surfaces. Further, the glycoprotein lubricin (LUB) was tested as an antiadhesive coating. Despite its hydrophilicity, the adsorption of peptides to LUB coated sensors was similar to the adsorption to unmodified gold surfaces, which indicates that some peptides diffused through the LUB layer to reach the underlying gold sensor surface. The LUB protein-antiadhesive is thus more effective as a biomaterial coating against larger biomolecules than small peptides under the conditions used here. This study provides directions toward a better understanding of amyloid peptide adsorption to biologically relevant interfaces, such as cellular membranes.

Comparative yields of antimicrobial peptides released from human and cow milk proteins under infant digestion conditions predicted by in silico methodology

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D3FO00748K

Abstract: Mammalian milk proteins are known to encrypt antimicrobial peptides (AMPs) which can be passively released and exert bioactivity in the gastrointestinal and cardiovascular systems pre- or post-absorption, respectively.

How kanamycin A interacts with bacterial and mammalian mimetic membranes

Publisher: Elsevier BV

Date: 11-2017

DOI: 10.1016/J.BBAMEM.2017.08.016

Abstract: Biological membranes are natural barriers to the transport of molecules and drugs within human bodies. Many antibacterial agents need to cross these membranes to reach their target and elicit specific effects. Kanamycin A belongs to the family of aminoglycoside antibiotics that target cellular RNA to inhibit bacterial and viral replication. Previous studies have shown that aminoglycosides bind to mammalian but disrupt bacterial membranes. In this study, molecular dynamics (MD) simulations and infrared (IR) spectroscopy were applied to investigate the initial, first key interactions of kanamycin A, as a representative aminoglycoside, with both bacterial and mammalian lipid bilayers at the molecular level. Computational studies revealed strong hydrogen bonding interactions between the hydroxyl and amino groups of the aminoglycoside with the ester carbonyl and phosphate groups of the lipids. IR spectroscopy provided experimental verification of the important role of the lipid's ester carbonyl, phosphate and hydroxyl groups for aminoglycoside binding. The bacterial membrane became disordered upon aminoglycoside addition, whereas the mammalian membrane became stiffer and more ordered. This indicates the bacterial membrane disruption observed by previous studies.

Helical Intermediate Formation and Its Role in Amyloid of an Amphibian Antimicrobial Peptide^†

Publisher: Cold Spring Harbor Laboratory

Date: 12-01-2023

DOI: 10.1101/2023.01.11.523545

Abstract: Helical intermediates appear to be crucial in amyloid formation of several amyloidogenic peptides, including A β , that are implicated in different neurodegenerative diseases. Intermediate species have been reported to be more toxic than mature amyloid fibrils. Hence, the focus of the current work is to understand both structural and mechanistic role of intermediates in the early stages of amyloid self-assembly in amyloidogenic peptides. Molecular dynamics (MD) simulations and the adaptive biasing force (ABF) method were utilized to investigate structural changes that lead to amyloid formation in hibian peptide uperin-3.5 (U3.5), an antimicrobial and amyloidogenic peptide. Microsecond time-scale MD simulations revealed that peptide aggregation, into β -sheet dominated aggregates, is centred on two important factors evolution of α -helical intermediates and the critical role of local peptide concentration inside these aggregates. Electrostatic attraction between the oppositely charged aspartate (D) and arginine (R) residues located near the N-terminus induced hydrogen bonding resulting in formation of precursor 3 10 -helices close to the N-terminus. The 3 10 -helices transitioned into α -helices, thereby imparting partial helical conformations to the peptides. In the initial stages of aggregation, U3.5 peptides with hipathic, partial helices aggregated to form small clusters of helical intermediates directed via hydrophobic interactions. These helices imparted stability to the helical intermediates, which promoted growth of clusters by further addition of peptides. This led to an increase in the local peptide concentration which enabled stronger peptide-peptide interactions and triggered a β -sheet transition in these aggregates. Thus, the study emphasized that stabilisation of peptide helical content may be crucial to the evolution of β -sheet-rich amyloid structures.

Lubricin: a versatile, biological anti-adhesive with properties comparable to polyethylene glycol.

Publisher: Elsevier BV

Date: 06-2015

DOI: 10.1016/J.BIOMATERIALS.2015.02.086

Abstract: Lubricin is a glycoprotein found in articular joints which has been recognized as being an important biological boundary lubricant molecule. Besides providing lubrication, we demonstrate, using a quartz crystal microbalance, that lubricin also exhibits anti-adhesive properties and is highly effective at preventing the non-specific adsorption of representative globular proteins and constituents of blood plasma. This impressive anti-adhesive property, combined with lubricin's ability to readily self-assemble to form dense, highly stable telechelic polymer brush layers on virtually any substrates, and its innate biocompatibility, makes it an attractive candidate for anti-adhesive and anti-fouling coatings. We show that coatings of lubricin protein are as effective as, or better than, self-assembled monolayers of polyethylene glycol over a wide range of pH and that this provides a simple, versatile, highly stable, and highly effective method of controlling unwanted adhesion to surfaces.

Electrochemical Characterization of Purified Rhus vernicifera Laccase:  Voltammetric Evidence for a Sequential Four-Electron Transfer

Publisher: American Chemical Society (ACS)

Date: 09-08-2003

DOI: 10.1021/BI034268P

Abstract: Rhus vernicifera (Rv) laccase was purified to electrophoretic homogeneity by hydrophobic interaction chromatography. A comprehensive study of the direct electrochemistry of Rv laccase covalently immobilized at a gold electrode using alkanethiol monolayers was undertaken. The observed midpoint potential was 410 mV versus the normal hydrogen electrode (NHE), consistent with reduction potentials obtained by potentiometric titration for the T1 copper site. Evidence is presented for a concerted 4-electron reversible process at slow scan rates (v) on the basis of peak current ratios (i(pa)/i(pc)). Catalytic currents were observed in the presence of the biological substrate oxygen, indicating that laccase activity is retained throughout the immobilization process. Electrochemical characteristics of the immobilized laccase were essentially invariant across the pH range 5.5-8.5 and the temperature range 5-35 degrees C. The purified enzyme displayed a pH optimum of 9.0, when assayed spectrophotometrically with syringaldazine as a substrate. Inhibition of the laccase activity with azide or fluoride showed an I(50)(NaN(3)) of 2.5 mM and an I(50)(NaF) of 18.5 mM. Electrochemistry in the presence of azide reduces the anodic current by ca. one-half, consistent with the 4-electron process decreasing to a 2-electron process. However, fluoride has no effect on anaerobic electrochemistry. These electrochemical results suggest that the pH dependence of laccase activity is related to the effects of pH on the structure or binding of the substrate.

Multifunctional protein nanocarriers for targeted nuclear gene delivery in nondividing cells

Publisher: Wiley

Date: 24-04-2009

DOI: 10.1096/FJ.09-131425

Abstract: Compartmentalization within eukaryotic cells hinders the efficient delivery of therapeutic agents to the cell nucleus. Here we describe novel multifunctional DNA carriers (MDCs) that self-assemble with DNA to form structured nanoparticles that possess virus-like functions for cellular trafficking. MDCs contain, in fusion, the DNA-compacting sperm chromatin component protamine, alpha-melanocyte-stimulating hormone for cell-targeted internalization, the endosome-translocation domain of diphtheria toxin, and an optimized nuclear localization sequence to confer recognition by the nuclear import machinery. The structure of the MDC-DNA particles was examined using atomic force microscopy, and the functionality of each domain assessed using in vitro techniques, including a reconstituted nuclear transport assay in semi-intact cells relying on the use of quantitative confocal laser scanning microscopy. The nanoparticles were internalized in cell-specific fashion and subsequently exited the endosome into the cytoplasm. Notably, the nanoparticles interact with cellular nuclear transport proteins as shown in direct binding assays and are actively trafficked into the cell nucleus of non iding cells, resulting in 3- to 4-fold higher reporter gene expression in growth-arrested human embryonic kidney cells, as well as lower cytotoxicity, than lipid and polyethyleneimine vectors. The importance of each functional domain was examined by comparing MDCs with different domain compositions as controls, as well as using antibodies to block particular pathways. MDCs that utilize cellular signaling pathways have enormous potential to safely and efficiently deliver therapeutic transgenes into the nucleus of non iding cells.

Api88 Is a Novel Antibacterial Designer Peptide To Treat Systemic Infections with Multidrug-Resistant Gram-Negative Pathogens

Publisher: American Chemical Society (ACS)

Date: 17-05-2012

DOI: 10.1021/CB300063V

Abstract: The emergence of multiple-drug-resistant (MDR) bacterial pathogens in hospitals (nosocomial infections) presents a global threat of growing importance, especially for Gram-negative bacteria with extended spectrum β-lactamase (ESBL) or the novel New Delhi metallo-β-lactamase 1 (NDM-1) resistance. Starting from the antibacterial peptide apidaecin 1b, we have optimized the sequence to treat systemic infections with the most threatening human pathogens, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The lead compound Api88 enters bacteria without lytic effects at the membrane and inhibits chaperone DnaK at the substrate binding domain with a K(D) of 5 μmol/L. The Api88-DnaK crystal structure revealed that Api88 binds with a seven residue long sequence (PVYIPRP), in two different modes. Mice did not show any sign of toxicity when Api88 was injected four times intraperitoneally at a dose of 40 mg/kg body weight (BW) within 24 h, whereas three injections of 1.25 mg/kg BW and 5 mg/kg BW were sufficient to rescue all animals in lethal sepsis models using pathogenic E. coli strains ATCC 25922 and Neumann, respectively. Radioactive labeling showed that Api88 enters all organs investigated including the brain and is cleared through both the liver and kidneys at similar rates. In conclusion, Api88 is a novel, highly promising, 18-residue peptide lead compound with favorable in vitro and in vivo properties including a promising safety margin.

(Pro(2)H(+))(2)(TCNQ(center dot-))(2)center dot TCNQ: an amino acid derived semiconductor

Publisher: Wiley

Date: 11-01-2011

DOI: 10.1002/ANGE.201005406

Mechanistic Insights Gained by Monitoring Carbon Nanotube/Prussian Blue Nanocomposite Formation With in Situ Electrochemically Based Techniques

Publisher: American Chemical Society (ACS)

Date: 06-06-2014

DOI: 10.1021/JP501442H

Interference from Trace Copper in Electrochemical Investigations Employing Carboxylic Acid Terminated Thiol Modified Gold Electrodes

Publisher: Wiley

Date: 03-2009

DOI: 10.1002/ELAN.200804462

{2-(4,7-Dimethyl-1,4,7-triazacyclonon-1-yl)-N-methyl-N-[(1-methylbenzimidazol-2-yl)methyl]ethylamine}-copper(II) bis(perchlorate)

Publisher: International Union of Crystallography (IUCr)

Date: 20-07-2001

DOI: 10.1107/S1600536801011540

Structural, Spectroscopic, and Electrochemical Characterization of Semi-Conducting, Solvated [Pt(NH3)4](TCNQ)2·(DMF)2 and Non-Solvated [Pt(NH3)4](TCNQ)2

Publisher: CSIRO Publishing

Date: 2017

DOI: 10.1071/CH17245

Abstract: The demand for catalysts that are highly active and stable for electron-transfer reactions has been boosted by the discovery that [Pt(NH3)4](TCNQF4)2 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) is an efficient catalyst. In this work, we prepare and characterize the two related [Pt(NH3)4]2+ complexes, [Pt(NH3)4](TCNQ)2·(DMF)2 (1) and [Pt(NH3)4](TCNQ)2 (2). Reaction of [Pt(NH3)4](NO3)2 with LiTCNQ in a mixed solvent (methanol/dimethylformamide, 4 : 1 v/v) gives [Pt(NH3)4](TCNQ)2·(DMF)2 (1), whereas the same reaction in water affords [Pt(NH3)4](TCNQ)2 (2). 2 has been previously reported. Both 1 and 2 have now been characterized by single-crystal X-ray crystallography, Fourier-transform (FT)IR, Raman and UV-vis spectroscopy, and electrochemistry. Structurally, in 1, the TCNQ1− anions form infinite stacks with a separation between adjacent anions within the stack alternating between 3.12 and 3.42 Å. The solvated structure 1 differs from the non-solvated form 2 in that pairs of TCNQ1− anions are clearly displaced from each other. The conductivities of pressed pellets of 1 and 2 are both in the semi-conducting range at room temperature. 2 can be electrochemically synthesized by reduction of a TCNQ-modified electrode in contact with an aqueous solution of [Pt(NH3)4](NO3)2 via a nucleation growth mechanism. Interestingly, we discovered that 1 and 2 are not catalysts for the ferricyanide and thiosulfate reaction. Li+ and tetraalkylammonium salts of TCNQ1−/2− and TCNQF41−/2− were tested for potential catalytic activity towards ferricyanide and thiosulfate. Only TCNQF41−/2− salts were active, suggesting that the dianion redox level needs to be accessible for efficient catalytic activity and explaining why 1 and 2 are not good catalysts. Importantly, the origin of the catalytic activity of the highly active [Pt(NH3)4](TCNQF4)2 catalyst is now understood, enabling other families of catalysts to be developed for important electron-transfer reactions.

Spontaneous redox synthesis of the charge transfer material TTF4[SVMo11O40]

Publisher: American Chemical Society (ACS)

Date: 12-11-2012

DOI: 10.1021/IC302045M

Abstract: The charge-transfer material TTF-SV(IV)Mo(11)O(40) (TTF = tetrathiafulvalene) was prepared by a spontaneous redox reaction between TTF and the vanadium-substituted polyoxometalate (n-Bu(4)N)(3)[SV(V)Mo(11)O(40)] in both solution and solid state phases. Single crystal X-ray diffraction gave the stoichiometry TTF(4)[SVMo(11)O(40)]·2H(2)O·2CH(2)Cl(2), with the single V atom positionally disordered with eight Mo atoms over the whole α-Keggin polyanion [SVMo(11)O(40)](4-). Raman spectra support the 1+ charge assigned to the oxidized TTF deduced from bond lengths, and elemental and voltammetric analysis also are consistent with this formulation. Scanning electron microscopy images showed a rod-type morphology for the new charge-transfer material. The conductivity of the solid at room temperature is in the semiconducting range. The TTF and (n-Bu(4)N)(3)[SV(V)Mo(11)O(40)] solids also undergo a rapid interfacial reaction, as is the case with TTF and TCNQ (TCNQ = tetracyanoquinodimethane) solids. EPR spectra at temperatures down to 2.6 K confirm the presence of two paramagnetic species, V(IV) and the oxidized TTF radical. Spectral evidence shows that the TTF-SV(IV)Mo(11)O(40) materials prepared from either solution or solid state reactions are equivalent. The newly isolated TTF-SV(IV)Mo(11)O(40) material represents a new class of TTF-polyoxometalate compound having dual electrical and magnetic functionality derived from both the cationic and anionic components.

Evolutionary comparisons predict that dimerization of human cytochrome P450 aromatase increases its enzymatic activity and efficiency

Publisher: Elsevier BV

Date: 11-2015

DOI: 10.1016/J.JSBMB.2015.09.006

Abstract: Estrogen is an essential vertebrate hormone synthesized from androgens involving multiple hydroxylations, catalyzed by cytochrome P450 aromatase (P450arom or CYP19) enzymes. Despite their importance, very few comparative studies have been conducted on vertebrate and/or mammalian P450arom enzymes, either structurally or functionally. Here we directly compared the human (h-) and porcine gonadal (p(g)-) P450arom, as p(g)-P450arom has very low catalytic efficiency, with a ten-fold higher affinity (Km) for a substrate (androstenedione) and ten-fold reduction in turnover (Vmax). We recombinantly expressed these proteins and compared their interactions on a membrane using a quartz crystal microbalance (QCM) and also with the electron donor protein cytochrome P450 oxidoreductase (CPR). Changes in frequency and dissipation in the QCM supported the h-P450arom forming a homodimer that agreed with the FRET data, but not p(g)-P450arom. Analysis of the X-ray crystal structure of the h-P450arom suggested a likely site of homo-dimerization and found that certain key interacting residues were not conserved in pg-P450arom. Molecular dynamics simulations provide support for the importance of these residues in homo-dimerization. Here we propose that the lower affinity and higher activity with reduced release of intermediate metabolites by the h-P450arom is as a consequence of its ability to form homodimers. The functional implications of dimerization provide an important mechanistic step in the requirement for efficient aromatization.

Tetrachlorido-1kCl,2k2 Cl,3kCl-bis[-μ-4-undecyl-1,4,7- triazacyclonon1-yl)acetato]-1k4 N,N′,N″,O: 2kO′;2kO′:-3k4 N,N′,N″,O-tricopper(II) dihydrate

Publisher: International Union of Crystallography (IUCr)

Date: 20-07-2007

DOI: 10.1107/S1600536807034538

Cholesterol and anionic phospholipids increase the binding of amyloidogenic transthyretin to lipid membranes

Publisher: Elsevier BV

Date: 2008

DOI: 10.1016/J.BBAMEM.2007.09.018

Abstract: Deposition of transthyretin (TTR) amyloid is a pathological hallmark of familial amyloidotic polyneuropathy (FAP). Recently we showed that TTR binds to membrane lipids via electrostatic interactions and that membrane binding is correlated with the cytotoxicity induced by amyloidogenic TTR. In the present study, we examined the role of lipid composition in membrane binding of TTR by a surface plasmon resonance (SPR) approach. TTR bound to lipid bilayers through both high- and low-affinity interactions. Increasing the mole fraction of cholesterol in the bilayer led to an increase in the amount of high-affinity binding of an amyloidogenic mutant (L55P) TTR. In addition, a greater amount of L55P TTR bound with high affinity to membranes made from anionic phospholipids, phosphatidylglycerol (PG) and phosphatidylserine (PS), than to membranes made from zwitterionic phospholipid phosphatidylcholine (PC). The anionic phospholipids (PS and PG) promoted the aggregation of L55P TTR by accelerating the nucleation phase of aggregation, whereas the zwitterionic phospholipid PC had little effect. These results suggest that cholesterol and anionic phospholipids may be important for TTR aggregation and TTR-induced cytotoxicity.

Lipid oxidation controls peptide self-assembly near membranes through a surface attraction mechanism

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D3SC00159H

Abstract: Oxidized model membranes have differential effects on peptide fibril formation, driven by surface attraction, peptide charge and secondary structure stabilization.

Structurally characterised vanadium(v)-substituted Keggin-type heteropolysulfates [SVM11O40]3− (M = Mo, W): voltammetric and spectroscopic studies related to the V(v)/V(iv) redox couple

Publisher: Royal Society of Chemistry (RSC)

Date: 2014

DOI: 10.1039/C3DT53161A

Abstract: Structures of the n-tetrabutylammonium salts of [SVM11O40](3-) (M = Mo, W) have been determined by X-ray crystallography and exhibit 3D networks with the V atom disordered over several sites. The cyclic voltammetric behavior of SVM11 in neutral and acidified acetonitrile solutions also has been investigated with respect to the V(V)/V(IV) couple. Results have been interpreted in conjunction with data provided by (51)V NMR spectroscopy on the oxidized V(V) form and by EPR spectroscopy on the reduced V(IV) form. Based on mechanistic details inferred from these studies, simulations of the cyclic voltammograms have been undertaken and results compared with experimental data in acidic media (two protonated forms) in order to provide estimates of equilibrium and kinetic parameters. For the V(V)/V(IV) couple in the series [XVM11O40](n-) (X = Si,Ge,P,As,S M = Mo,W), the reversible potentials in neutral acetonitrile linearly depend on the total charge of the vanadium-substituted polyoxometalates, similar to the dependence previously reported for the non-substituted parent Keggin polyoxometalates [XM12O40](m-).

Crystal and molecular structure of the peroxo-bridged dimer [(trenen)CoO2Co(trenen)] (ClO4)4 where trenen = n, n, n'-tris(2-aminoethyl)-ethane-1,2-diamine

Publisher: CSIRO Publishing

Date: 1991

DOI: 10.1071/CH9910351

Abstract: The preparation and crystal structure of the brown crystalline cobalt(III) dimer [( trenen )CoO2-Co( trenen )](ClO4)4 is described where the pentadentate ligand trenen is N,N,N′- tris (2-aminoethyl)ethane-1,2-diamine. The compound forms monoclinic crystals with a 13.132, b 14.214, c 8.906Ǻ and β 91.53°, and two formula units in the unit cell, in space group P21/n. The nitrogen atoms of the trenen ligand occupy five of the six slightly distorted octahedral sites about each cobalt atom with a peroxo bridge linking the two Co( trenen ) moieties through the sixth site. The Co-O-O-Co dihedral angle is 180°, the molecule possesses a centre of symmetry, and the peroxo bridging group is situated trans to the secondary nitrogen atom attached to each cobalt atom (the s,s -isomer). The electronic spectrum displays a strong (є 13700 dm3 mol-1 cm-1) absorption band at 302 nm which is typical of peroxo -bridged dicobalt complexes with a single transplanar CoO2Co bridge.

Synthesis and characterization of a stable hexa-amine vanadium(IV) cage complex

Publisher: Royal Society of Chemistry (RSC)

Date: 1985

DOI: 10.1039/C39850000174

Critical effects of polar fluorescent probes on the interaction of DHA with POPC supported lipid bilayers

Publisher: Elsevier BV

Date: 05-2018

DOI: 10.1016/J.BBAMEM.2018.01.013

Abstract: The understanding of lipid bilayer structure and function has been advanced by the application of molecular fluorophores. However, the effects of these probe molecules on the physicochemical properties of membranes being studied are poorly understood. A quartz crystal microbalance with dissipation monitoring instrument was used in this work to investigate the impact of two commonly used fluorescent probes, 1‑palmitoyl‑2‑{12‑[(7‑nitro‑2‑1,3‑benzoxadiazol‑4‑yl)amino]dodecanoyl}‑sn‑glycero‑3‑phosphocholine (NBD-PC) and 1,2‑dipalmitoyl‑sn‑glycero‑3‑phosphoethanolamine‑n‑(lissamine rhodamine‑B‑sulfonyl) (Lis-Rhod PE), on the formation and physicochemical properties of a 1‑palmitoyl‑2‑oleoyl‑sn‑glycero‑3‑phosphocholine supported lipid bilayer (POPC-SLB). The interaction of the POPC-SLB and fluorophore-modified POPC-SLB with docosahexaenoic acid, DHA, was evaluated. The incorporation of DHA into the POPC-SLB was observed to significantly decrease in the presence of the Lis-Rhod PE probe compared with the POPC-SLB. In addition, it was observed that the small concentration of DHA incorporated into the POPC:NBD-PC SLB can produce rearrangement processes followed by the lost not only of DHA but also of POPC or NBD-PC molecules or both during the washing step. This work has significant implications for the interpretation of data employing fluorescent reporter molecules within SLBs.

A study of protein electrochemistry on a supported membrane electrode

Publisher: Springer Science and Business Media LLC

Date: 12-04-2006

DOI: 10.1007/S10989-006-9029-0

A Systematic (Spectro-) Electrochemical Approach to the Synthesis and Characterisation of Co(II) and Ni(II) Compounds Containing Reduced Forms of TCNQF

Publisher: Wiley

Date: 08-2018

DOI: 10.1002/CELC.201800678

Vesicular disruption of lysosomal targeting organometallic polyarginine bioconjugates

Publisher: Oxford University Press (OUP)

Date: 2015

DOI: 10.1039/C4MT00255E

Abstract: Targeting of lysosomes is an interesting, novel pathway for cancer therapy. in this work, novel metallocene derivatives (of ferrocene and ruthenocene) of a cell penetrating polyarginine peptide are presented as lysosomal membrane permeabilization (LMP) agents and their localization and biological activity is investigated in detail.

Characterisation of a coordinated imidazole as a structural model for superoxide dismutase

Publisher: Elsevier BV

Date: 10-2002

DOI: 10.1016/S1387-7003(02)00557-9

Revisiting the TCNQF40/1−/2− Catalysis Mechanism for the [Fe(CN)6]3−/4−‐S2O32−/S4O62− Redox Reaction

Publisher: Wiley

Date: 19-04-2023

DOI: 10.1002/CPHC.202200942

Abstract: Published data suggest that sparingly soluble metal complexes of , where n=0, 1, 2, 4, can act as heterogeneous catalysts for the kinetically very slow ‐ / reaction in aqueous solution. This study shows that the coordination polymer , participates as a homogeneous catalyst via an extremely small concentration of dissolved . This finding suggests that the generally accepted mechanism of catalysis by based solids needs to be revisited to ascertain the role of homogeneous pathways. In the present study, UV‐visible spectrophotometry was used to examine the catalysis of the aqueous redox reaction of (1.0 mM) with (100 mM) in the presence of (i) a precursor catalyst, (ii) the catalyst, , as the water soluble Li + salt and (iii) . A homogeneous reaction scheme that utilises the couple is provided. In the case of derived from highly soluble , quantitative conversion of 1.0 mM to 0.50 mM occurs with complete reduction of to being rapidly accelerated by sub‐micomolar concentrations of . generated in the catalytic cycle, reacts with to reform and produce . Along with the rapid catalytic reaction, the sluggish competing reaction between and occurs to give , which is protonated to , along with a trace amount of . On addition of the precursor catalyst, , rapid reduction with occurs to form – the active catalyst. added to water is shown to be sufficiently soluble to provide adequate to act as the catalyst for the ‐ / reaction.

Tunable Biogenic Manganese Oxides

Publisher: Wiley

Date: 28-08-2017

DOI: 10.1002/CHEM.201702579

Abstract: Influence of the conditions for aerobic oxidation of Mn2+(aq) catalysed by the MnxEFG protein complex on the morphology, structure and reactivity of the resulting biogenic manganese oxides (MnO

β‐Amyloid protein oligomers induced by metal ions and acid pH are distinct from those generated by slow spontaneous ageing at neutral pH

Publisher: Wiley

Date: 16-10-2003

DOI: 10.1046/J.1432-1033.2003.03815.X

Abstract: Amyloid protein (Abeta1-40) aggregation and conformation was examined using native and sodium dodecyl sulfate olyacrylamide gel electrophoresis, and the results compared with those obtained by atomic force microscopy, and with Congo red binding, sedimentation and turbidity assays. The amount of Abeta aggregation measured was different, depending upon the method used. Incubation for 15 min at pH 5.0 or in the presence of Fe2+, Cu2+ or Zn2+ did not alter the level of Abeta oligomers observed on SDS and native gels. However, the slow aggregation of Abeta to form high molecular mass species over 5 days was inhibited. In contrast, when Abeta aggregation was monitored using a Congo red binding assay or sedimentation assay, a rapid increase in Abeta aggregation was observed after incubation for 15 min at pH 5.0, or in the presence of Fe2+, Cu2+ or Zn2+. The low pH-, Zn2+- or Cu2+-induced Abeta aggregation measured in a turbidity assay was reversible. In contrast, a considerable proportion of the Abeta aggregation measured by native and SDS/PAGE was stable. Atomic force microscopy studies showed that Abeta aged at pH 5.0 or in the presence of Zn2+ produced larger looser rod-shaped aggregates than at pH 7.4. Abeta that had been aged at pH 7.4 was more cytotoxic than Abeta aged at pH 5.0. Taken together, the results suggest that Abeta oligomerizes via two mutually exclusive mechanisms to form two different types of aggregates, which differ in their cytotoxic properties.

Electrochemically Directed Synthesis of Cu2I(TCNQF4II–)(MeCN)2 (TCNQF4 = 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane): Voltammetry, Simulations, Bulk Electrolysis, Spectroscopy, Photoactivity, and X-ray Crystal Structure of the Cu2I(TCNQF4II–)(EtCN)2 Analogue

Publisher: American Chemical Society (ACS)

Date: 25-02-2014

DOI: 10.1021/IC500225V

Lubricin Antiadhesive Coatings Exhibit Size-Selective Transport Properties that Inhibit Biofouling of Electrode Surfaces with Minimal Loss in Electrochemical Activity

Publisher: Wiley

Date: 05-02-2018

DOI: 10.1002/ADMI.201701296

Fourier-Transformed Large-Amplitude AC Voltammetric Study of Tetrathiafulvalene (TTF): Electrode Kinetics of the TTF0/TTFC center dot+ and TTFC center dot+/TTF2+ Processes

Publisher: Wiley

Date: 06-11-2014

DOI: 10.1002/CELC.201300129

Electrochemical Investigation of the Oxidation of Thiosulfate by 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane and Its Anion Radical

Publisher: Wiley

Date: 13-12-2021

DOI: 10.1002/CELC.202101232

Abstract: The oxidation of thiosulfate has been of interest for more than a century, including the famous oscillating iodine clock reaction. From a thermodynamic perspective, calculations based on the reversible potentials reveal that both neutral TCNQF 4 0 (2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane) or its radical anion (TCNQF 4 1− ) can oxidize thiosulfate to tetrathionate to form TCNQF 4 2− . The reaction of S 2 O 3 2− with TCNQF 4 0 in a 2:1 or greater concentration ratio occurs in a step‐wise fashion to initially (and rapidly) form S 4 O 6 2− and TCNQF 4 1− (reaction 1), followed by a slow step involving the oxidation of residual S 2 O 3 2− by TCNQF 4 1− to give more S 4 O 6 2− and TCNQF 4 2− (reaction 2). Thus, this reaction occurs in two, temporally well‐resolved, steps with dramatically different kinetics. If S 2 O 3 2− and TCNQF 4 1− are mixed in a 1 : 1 ratio, then S 4 O 6 2− and TCNQF 4 2− are formed quantitatively on the same (hours) timescale, as for the second (slow) step described above. There is no evidence of further oxidation of S 4 O 6 2− to SO 4 2− . A slight increase in the rate of reaction 2 was observed in the presence of Bu 4 NPF 6 and attributed to ion‐pairing effects. Interestingly, during voltammetric experiments, if the Pt counter electrode is not separated from the reaction solution via a salt bridge, reaction 2 is catalyzed. The rates of reaction 2 have been studied over a wide range of conditions. Intriguingly, the mechanisms are dependent on whether S 2 O 3 2− or TCNQF 4 1− (much faster) are in excess. With S 2 O 3 2− in excess, the rate of reaction is first‐order in both S 2 O 3 2− and TCNQF 4 1− . With TCNQF 4 1− in excess, the reaction is more complicated with indications of Li + catalysis through electrostatic shielding of the TCNQF 4 1− and/or S 2 O 3 2− reactants. The large difference in rate of reaction of TCNQF 4 0 /S 2 O 3 2− (rapid) compared with TCNQF 4 1− /S 2 O 3 2− (sluggish) is in part attributable to the much larger driving force in the former case. All experimental studies were undertaken in the mixed solvent system, acetonitrile (MeCN) containing 5 % water, v/v (95 % MeCN : 5 % water) where all the reactants and products are soluble and stable. Voltammetric analysis using steady‐state (microdisc) or transient cyclic voltammetry (macrodisc) with electrolyte (Bu 4 NPF 6 ) and UV‐visible spectrophotometry with or without electrolyte were used to monitor the time dependence and establish the identity of the products.

Interactions between Lubricin and Hyaluronic Acid Synergistically Enhance Antiadhesive Properties.

Publisher: American Chemical Society (ACS)

Date: 26-04-2019

DOI: 10.1021/ACSAMI.9B01493

Abstract: Preventing the unwanted adsorption of proteins and cells at articular cartilage surfaces plays a critical role in maintaining healthy joints and avoiding degenerative diseases such as osteoarthritis. Immobilized at the surface of healthy articular cartilage is a thin, interfacial layer of macromolecules consisting mainly of hyaluronic acid (HA) and lubricin (LUB a.k.a. PRG4) that is believed to form a co-adsorbed, composite film now known to exhibit synergistic tribological properties. Bioinspired by the composition of cartilage surfaces, composite layers of HA and LUB were grafted to Au surfaces and the antiadhesive properties were assessed using surface plasmon resonance and quartz crystal microbalance. A clear synergistic enhancement in antiadhesive properties was observed in the composite films relative to grafted HA and LUB layers alone. Atomic force microscopy (AFM) normal force measurements provide insight into the architecture of the HA/LUB composite layer and implicate a strong contribution of hydrophobic interactions in the binding of LUB end-domains directly to HA chains. These AFM force measurements indicate that the adhesion of LUB to HA is strong and indicate that the hydrophobic coupling of LUB to HA shields the hydrophobic domains in these molecules from interactions with other proteins or molecules.

Use of optical interferometry to measure gold nanoparticle adsorption on silica

Publisher: Elsevier BV

Date: 10-2016

DOI: 10.1016/J.COLSURFA.2016.07.022

An extrusion strategy for the FeMo cofactor from nitrogenase: Towards synthetic iron-sulfur proteins

Publisher: Wiley

Date: 15-11-2001

DOI: 10.1046/J.0014-2956.2001.02506.X

Abstract: Iron-sulfur clusters are ubiquitous in biological systems, facilitating functions such as electron transfer (rubredoxins, ferredoxins, rieske centres), isomerization (aconitase) and small molecule activation such as dinitrogen reduction (nitrogenases). Of global importance and recently particular interest, is the iron-sulfur-containing iron-molybdenum cofactor (FeMoco) cluster that achieves the biological reduction of dinitrogen under mild conditions. This biologically unique cluster has proved difficult to investigate due to its extreme air sensitivity and the instability of the cluster's structural integrity, outside the protective protein matrix. Here, we report a model iron-sulfur cluster (Roussins black salt (NH(4))[Fe(4)S(3)(NO)(7)]) that has been used to achieve the first ex le of a metal cluster (guest) embedded within a pseudo-protein, cyclodextrin (host). The product formed is supramolecular, that is, it contained no covalent bonds and was stabilized by predominantly entropy effects. Formation of a 1 : 1 complex between the host and the guest was established for the iron-sulfur cluster with either seven- or eight-membered cyclodextrins (beta- or gamma-cyclodextrin). A range of techniques was used to characterize the new complexes in both the solid and solution states. Electrospray mass spectra indicated the presence of parent ions of the host-guest complexes and electrochemistry was also used to define the redox behavior of the complexes. The iron-sulfur clusters were significantly more stable in the presence of the host cyclodextrin, as revealed by a negative shift for the reduction potential for the host-guest product. Using the beta-cyclodextrin as host, the reduction potential of the iron-sulfur cluster shifted more negative by 60 mV the effect was even more dramatic for the larger gamma-cyclodextrin where the reduction potential for the cluster was shifted by 90 mV more negative than the 'unbound' [Fe(4)S(3)(NO)(7)]- cluster. This is the first ex le of a metal cluster, stabilized as a supramolecular complex in a 'host' environment outside of a covalently bonded protein matrix. Creating such stable environments for metal cofactors or clusters that otherwise spontaneously degrade or are catalytically inactive outside the protein matrix could have enormous practical value. Specific implications for the development of extrusion methods for FeMoco from nitrogenase are enormous, with previously difficult, high-energy molecular transformations, such as dinitrogen to ammonia, now more realistically accessible.

Membrane interaction and selectivity of novel alternating cationic lipid-nanodisc assembling polymers

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D3BM00477E

Abstract: The polymer–lipid nanodisc forming ability of a novel class of hipathic copolymer comprised of an alternating sequence was established. Selective membrane disruption was shown to be tuneable in relation to polymer hydrophobicity.

Reconstitution of a nanomachine driving the assembly of proteins into bacterial outer membranes

Publisher: Springer Science and Business Media LLC

Date: 24-10-2014

DOI: 10.1038/NCOMMS6078

A systematic study of the variation of tetrathiafulvalene (TTF), TTF⁺˙ and TTF²⁺ reaction pathways with water in the presence and absence of light

Publisher: Royal Society of Chemistry (RSC)

Date: 2014

DOI: 10.1039/C4RA08038F

Abstract: The chemistry of TTF 0/+/2+ and HTTF + in acetonitrile/water uses different reaction pathways e.g. illumination of TTF + oxidises water to O 2 .

Front Cover: Revisiting the TCNQF40/1−/2− Catalysis Mechanism for the [Fe(CN)6]3−/4−‐S2O32−/S4O62− Redox Reaction (ChemPhysChem 11/2023)

Publisher: Wiley

Date: 06-2023

DOI: 10.1002/CPHC.202300324

Transthyretin oligomers induce calcium influx via voltage-gated calcium channels

Publisher: Wiley

Date: 25-08-2007

DOI: 10.1111/J.1471-4159.2006.04210.X

Abstract: The deposition of transthyretin (TTR) amyloid in the PNS is a major pathological feature of familial amyloidotic polyneuropathy. The aim of the present study was to examine whether TTR could disrupt cytoplasmic Ca(2+) homeostasis and to determine the role of TTR aggregation in this process. The aggregation of amyloidogenic TTR was examined by solution turbidity, dynamic light scattering and atomic force microscopy. A nucleation-dependent polymerization process was observed in which TTR formed low molecular weight aggregates (oligomers < 100 nm in diameter) before the appearance of mature fibrils. TTR rapidly induced an increase in the concentration of intracellular Ca(2+) ([Ca(2+)](i)) when applied to SH-SY5Y human neuroblastoma cells. The greatest effect on [Ca(2+)](i) was induced by a preparation that contained the highest concentration of TTR oligomers. The TTR-induced increase in [Ca(2+)](i) was due to an influx of extracellular Ca(2+), mainly via L- and N-type voltage-gated calcium channels (VGCCs). These results suggest that increasing [Ca(2+)](i) via VGCCs may be an important early event which contributes to TTR-induced cytotoxicity, and that TTR oligomers, rather than mature fibrils, may be the major cytotoxic form of TTR.

Revisiting the TCNQF40/1−/2− Catalysis Mechanism for the [Fe(CN)6]3−/4−‐S2O32−/S4O62− Redox Reaction

Publisher: Wiley

Date: 06-2023

DOI: 10.1002/CPHC.202300323

Abstract: The front cover artwork was done by Michelle Farrelly, a member of the Martin group at Monash University. The image represents a perspective of a cuvette in which the catalysis of the thiosulfate‐ferricyanide reaction was achieved by a TCNQF 4 ‐based redox reaction in aqueous solution. The primary method used to monitor these reactions was spectrophotometry. Read the full text of the Research Article at 10.1002/cphc.202200942 .

Biogenic Manganese-Oxide Mineralization is Enhanced by an Oxidative Priming Mechanism for the Multi-Copper Oxidase, MnxEFG

Publisher: Wiley

Date: 21-12-2017

DOI: 10.1002/CHEM.201603803

Abstract: In a natural geochemical cycle, manganese-oxide minerals (MnO

[1,4,7-Tris(3-tert-butyl-5-methyl-2-hydroxybenzyl)-1,4,7- triazacyclononanato-N,N′,N″,-O,O′,O″]chromium(III)

Publisher: International Union of Crystallography (IUCr)

Date: 15-01-1999

DOI: 10.1107/S0108270198010956

Fluorine Substitution of TCNQ Alters the Redox‐Driven Catalytic Pathway for the Ferricyanide‐Thiosulfate Reaction

Publisher: Wiley

Date: 15-09-2023

DOI: 10.1002/CPHC.202300289

Live bio-nano-sonosensitizer targets malignant tumors in synergistic therapy

Publisher: Elsevier BV

Date: 2023

DOI: 10.1016/J.ACTBIO.2022.11.037

Abstract: Sonosensitizers that can increase the concentration of reactive oxygen species (ROS) within a tumor microenvironment is a high priority for sonodynamic therapy (SDT). In this study, a functionalized, smart nanosonosensitizer based on Au-RuO

Recent progress in cytochrome P450 enzyme electrochemistry

Publisher: Informa Healthcare

Date: 21-07-2006

DOI: 10.1517/17425255.2.4.581

Abstract: Cytochrome P450 (CYP) enzymes perform crucial functions in humans, including the metabolism of drugs and hormone synthesis. The catalytic reactions performed by these enzymes (typically monoxygenation) require the transfer of electrons. Thermodynamic and mechanistic detail of the electron transfer component of these catalytic processes has been obtained traditionally from potentiometric titrations. More recently, voltammetric approaches (that are inherently simpler and require less s le) have been used. This has been made possible by the creation of biocompatible electrode surfaces at which the P450 enzyme is confined and able to undergo physiologically relevant electron transfer processes. The continuing challenge has been to obtain an in vivo-like enzyme response, and to provide the basis for the creation of an artificial bioprocess in vitro. A powerful instrumental electrochemical method, employing Fourier-transformed large- litude ac voltammetry, offers the potential for greater insight and new opportunities to understand the nuances of the electron transfer process. This review highlights several recent advances in the electrochemistry of P450 enzymes rather than providing a comprehensive review of P450 electrochemistry.

Use of the TCNQF₄²⁻ Dianion in the Spontaneous Redox Formation of [Fe^III(L⁻)₂][TCNQF₄^⋅−]

Publisher: Wiley

Date: 09-03-2018

DOI: 10.1002/CPLU.201800010

Abstract: The reaction of [Fe

Spin equilibria in iron(II) hexa-amine cages

Publisher: Royal Society of Chemistry (RSC)

Date: 1988

DOI: 10.1039/C39880001313

The origin of secondary structure transitions and peptide self-assembly propensity in trifluoroethanol-water mixtures

Publisher: Cold Spring Harbor Laboratory

Date: 17-09-2023

DOI: 10.1101/2023.09.14.557831

Reconstitution of Membrane Proteins into Model Membranes: Seeking Better Ways to Retain Protein Activities

Publisher: MDPI AG

Date: 14-01-2013

DOI: 10.3390/IJMS14011589

Electrochemical quartz crystal microbalance study of azurin adsorption onto an alkanethiol self-assembled monolayer on gold

Publisher: American Chemical Society (ACS)

Date: 28-11-2008

DOI: 10.1021/LA702511W

Abstract: A quartz crystal microbalance coupled with electrochemistry was used to examine the adsorption of azurin on a gold electrode modified with a self-assembled monolayer of octanethiol. Azurin adsorbed irreversibly to form a densely packed monolayer. The rate of azurin adsorption was related to the bulk concentration of azurin in solution within the concentration range studied. At a high azurin concentration (2.75 muM), adsorption was rapid with a stable adsorption maximum attained in 2-3 min. At a lower azurin solution concentration (0.35 muM), the time to reach a stable adsorption maximum was approximately 30 min. Interestingly, the maximum surface concentration attained for all solution concentrations studied by the QCM method was 25 +/- 1 pmol cm-2, close to that predicted for monolayer coverage. The dissipation was monitored during adsorption, and only small changes were detected, implying a rigid adsorption model, as needed when using the Sauerbrey equation. Cyclic voltammetric data were consistent with a one-electron, surface-confined CuII/CuI azurin process with fast electron-transfer kinetics. The electroactive surface concentration calculated using voltammetry was 7 +/- 1 pmol cm-2. The differences between the QCM and voltammetrically determined surface coverage values reflect, predominantly, the different measurement methods but imply that all surface-confined azurin is not electrochemically active on the time scale of cyclic voltammetry.

Self‐Assembly of Linear, Natural Antimicrobial Peptides: An Evolutionary Perspective

Publisher: Wiley

Date: 05-10-2022

DOI: 10.1002/CPLU.202200240

Abstract: Antimicrobial peptides are an ancient and innate system of host defence against a wide range of microbial assailants. Mechanistically, unstructured peptides undergo a secondary structure transition into hipathic α‐helices, upon contact with membrane surfaces. This leads to peptide binding and removal of the membrane components in a detergent‐like manner or via self‐organisation into trans‐membrane pores (either barrel‐stave or toroidal pore) thereby destroying the microbe. Self‐assembly of antimicrobial peptides into oligomers and ultimately amyloid has been mostly examined in parallel, however recent findings link diseases, such as Alzheimer's disease as an aberrant activity of a protective neuropeptide with antimicrobial activity. These self‐assembled oligomers can also interact with membranes. Here, we review those antimicrobial peptides reported to self‐assemble into amyloid, where supported by structural evidence. We consider their membrane activities as antimicrobial peptides and present evidence of consistent self‐assembly patterns across major evolutionary groups. Trends are apparent across these groups, supporting the mounting data that self‐assembly of antimicrobial peptides into amyloid should be considered as synergistic to the antimicrobial peptide response.

The influence of promoter and of electrode material on the cyclic voltammetry of Pisum sativum plastocyanin

Publisher: Elsevier BV

Date: 12-2002

DOI: 10.1016/S1567-5394(02)00125-1

Abstract: The reversible cyclic voltammetry of pea plastocyanin (Pisum sativum) was studied with a wide range of electrodes: edge-oriented pyrolytic graphite (PGE), glassy carbon (GCE), gold (Au) and platinum (Pt) electrodes. Plastocyanin was coated onto the electrode surface by exploiting the electrostatic interaction between the negatively charged protein and a wide range of positively charged promoters. The effect of the redox response with an extended range of promoters, including poly-L-lysine, polymyxin B, neomycin, tobramycin, geneticin, spermine and spermidine, were included in this study. The resulting cyclic voltammograms reveal that the observed midpoint potential for plastocyanin can be shifted significantly depending on the choice of promoter. The stability of the negatively charged plastocyanin-promoter layer on an electrode was gauged by the rate of bulk diffusion of the protein from the immobilised film into the solution. Reversible cyclic voltammograms were obtained using edge-oriented pyrolytic graphite (PGE) and glassy carbon electrodes (GCE) with all promoters however, platinum and gold electrodes were unable to sustain a defined redox response. The combination of pyrolytic graphite electrode oly-L-lysine lastocyanin was found to be the most stable combination, with a redox response which remained well defined in solution for more than 1 h at pH 7.0. The midpoint potentials obtained in this manner differed between the two graphite electrodes PGE and GCE using poly-L-lysine as the promoter. This effect was in addition to the expected pH dependence of the midpoint potential for plastocyanin and the results indicated that the pK(a) for plastocyanin on PGE was 4.94 compared to that on GCE of 4.66. It is concluded that both the electrode material and the nature of the promoter can influence the position of the redox potentials for proteins measured in vitro. This study extends the range of biogenic promoters used in combination with electrode materials. Thus, we can begin to develop a more comprehensive understanding of electrode-protein interactions and draw conclusions as to metalloprotein function, in vivo. To support these studies, we have sought information as to the nature of the electrode romoter rotein interaction using scanning tunneling microscopy (STM) to study both the promoter and the plastocyanin protein on a gold surface.

Chiral Tetraamines Based on (S)‐2‐(Aminomethyl)pyrrolidine: Template synthesis and properties of copper(II) complexes

Publisher: Wiley

Date: 05-02-1992

DOI: 10.1002/HLCA.19920750111

Synthesis, Physical Properties, Structural, and Electrochemical Characterization of Methimidazolium and Imidazolium-based Tetracyanoquinodimethane Anion Radical Salts

Publisher: CSIRO Publishing

Date: 2011

DOI: 10.1071/CH11044

Abstract: Two methimazolium and two imidazolium-based salts derived from combination with the tetracyanoquinodimethane (TCNQ) radical anion have been synthesized (1–4). The 1:1 (cation:anion) stoichiometry of the chemically synthesized materials is fully supported by steady-state voltammetric measurements at a microdisc electrode in acetonitrile. The methimazolium TCNQ salts (1 and 2), which contain an acidic proton on the cation, exhibit a protonation step coupled to the TCNQ1–/2– charge-transfer process. Solid–solid transformations at a TCNQ-modified electrode also lead to electrochemical synthesis of 1–4, but also indicate that other cation:anion stoichiometries are accessible. Atomic force microscopy for electrochemically synthesized s les exhibit rod-like morphology. Conductivity measurements on chemically and electrochemically prepared salts are in the semiconducting range. Scanning electrochemical microscopy approach curve data support the substantial conductivity of these solids. Extensive physicochemical characterization of these materials is in complete accordance with the X-ray crystal structure of 1-acetonitrile-3-methylimidazolium tetracyanoquinodimethane, [AMim+][TCNQ1–], 4.

Oncocin (VDKPPYLPRPRPPRRIYNR-NH₂): A Novel Antibacterial Peptide Optimized against Gram-Negative Human Pathogens

Publisher: American Chemical Society (ACS)

Date: 21-06-2010

DOI: 10.1021/JM100378B

Abstract: Small proline-rich antimicrobial peptides (AMP) have attracted considerable interest, as they target specific intracellular bacterial components and do not act by lytic mechanisms. Here, a novel peptide, termed oncocin (VDKPPYLPRPRPPRRIYNR-NH(2)), is reported that was optimized for the treatment of Gram-negative pathogens. Its minimal inhibitory concentrations in tryptic soy broth medium ranged from 0.125 to 8 microg/mL for 34 different strains and clinical isolates of Enterobacteriaceae and nonfermenters, such as Escherichia coli , Pseudomonas aeruginosa , and Acinetobacter baumannii . Substitutions of two arginine residues by ornithine increased the half-lives in full mouse serum from about 20 min to greater than 180 min and the activity. Both optimized oncocin derivatives were neither toxic to human cell lines nor hemolytic to human erythrocytes. They could freely penetrate lipid membranes and were washed out completely without any sign of lytic activity, as assessed by quartz crystal microbalance. Fluorescence labeled peptides entered the periplasmic space within 20 min at room temperature and homogeneously stained E. coli within 50 min. In conclusion, the optimized oncocin represents a very promising candidate for future in vivo work and may serve as a novel lead compound for an antibacterial drug class.

Surface Immobilization of Bio-Functionalized Cubosomes: Sensing of Proteins by Quartz Crystal Microbalance

Publisher: American Chemical Society (ACS)

Date: 09-12-2012

DOI: 10.1021/LA2032994

Abstract: A strategy for tethering lipid liquid crystalline submicrometer particles (cubosomes) to a gold surface for the detection of proteins is reported. Time-resolved quartz crystal microbalance (QCM-D) was used to monitor the cubosome-protein interaction in real time. To achieve specific binding, cubosomes were prepared from the nonionic surfactant phytantriol, block-copolymer, Pluronic F-127, and a secondary biotinylated lipid, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl(polyethyleneglycol)-2000], which enabled attachment of the particles to a neutravidin (NAv)-alkanethiol monolayer at the gold surface of the QCM sensor chip. A second set of cubosomes was further functionalized with addition of the glycolipid (G(M1)) to facilitate a specific binding uptake of the protein, cholera toxin B subunit (CT(B)), from solution. QCM-D confirmed the specificity of the cubosome-NAv binding. The analysis of titration experiments, also performed with QCM, suggests that an optimal concentration of cubosomes is required for the efficient packing of the particles at the surface: high cubosome concentrations lead to chaotic cubosome binding onto the surface, sterically inhibiting surface attachment, or require significant reorganization to permit uniform cubosome coverage. The methodology enabled the straightforward preparation of a complex nanostructured edifice, which was then used to specifically capture analyte proteins (cholera toxin B subunit or free NAv) from solution, supporting the potential for development of this approach as a biosensing platform.

Spatially-resolved bioelectrochemistry with scanning electrochemical cell microscopy: A microscale study of coenzyme Q10 modified carbon electrodes

Publisher: Elsevier BV

Date: 12-2023

DOI: 10.1016/J.ELECTACTA.2023.143362

Direct electrochemistry of human, bovine and porcine cytochrome P450c17

Publisher: Bioscientifica

Date: 04-2006

DOI: 10.1677/JME.1.01971

Abstract: The direct electrochemistry of human, bovine and porcine cytochrome P450c17 (CYP17) has been examined on an edge-oriented pyrolytic graphite electrode. The recombinant protein was immobilized on an electrode modified with a surfactant to simulate the environment of a biological membrane, and hence physiological electron-transfer conditions. The P450 enzymes all retained ‘electron-transfer’ activity while immobilized at the electrode surface as assessed by the presence of catalytic signals under aerobic conditions. The redox potentials for porcine P450c17 were more positive (anodic) than both the human and bovine forms, perhaps reflecting the differences in substrate specificity for these species. In addition, these enzymes were all influenced by pH, consistent with a single proton associated with the single electron-transfer event. Ionic strength of the buffer medium also shifted the redox potentials towards positive, suggesting that electrostatic forces contribute to the protein environment required for the electron-transfer process. The effect of substrate on the redox potential for each P450c17 was measured in the presence of pregnenolone, progesterone, 17α-hydroxypregnenolone and 17α-hydroxyprogesterone. However, no influence on the redox parameters was observed.

Systematic and non-systematic substituent effects gleaned from studies on CuTCNQFn (n = 0, 1, 2, 4): Electrocrystallisation and characterisation of CuTCNQF

Publisher: Elsevier BV

Date: 05-2020

DOI: 10.1016/J.ICA.2020.119458

Mechanistic insight into the early stages of amyloid formation using an anuran peptide

Publisher: Wiley

Date: 17-05-2019

DOI: 10.1002/PEP2.24120

Single-molecule imaging of amyloid-beta protein (Abeta) of Alzheimer's disease: from single-molecule structures to aggregation mechanisms and membrane interactions

Publisher: Elsevier

Date: 2014

DOI: 10.1016/B978-0-12-394431-3.12001-2

Role of Aβ and the α7 nicotinic acetylcholine receptor in regulating synaptic plasticity in Alzheimer's disease

Publisher: Springer Science and Business Media LLC

Date: 09-2003

DOI: 10.1007/BF02442570

Role of cytochrome b5 in the modulation of the enzymatic activities of cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1)

Publisher: Elsevier BV

Date: 06-2017

DOI: 10.1016/J.JSBMB.2016.02.033

Abstract: Cytochrome b5 (cyt b5) is a small hemoprotein that plays a significant role in the modulation of activities of an important steroidogenic enzyme, cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1, CYP17A1). Located in the zona fasciculata and zona reticularis of the adrenal cortex and in the gonads, P450 17A1 catalyzes two different reactions in the steroidogenic pathway the 17α-hydroxylation and 17,20-lyase, in the endoplasmic reticulum of these respective tissues. The activities of P450 17A1 are regulated by cyt b5 that enhances the 17,20-lyase reaction by promoting the coupling of P450 17A1 and cytochrome P450 reductase (CPR), allosterically. Cyt b5 can also act as an electron donor to enhance the 16-ene-synthase activity of human P450 17A1. In this review, we discuss the many roles of cyt b5 and focus on the modulation of CYP17A1 activities by cyt b5 and the mechanisms involved.

[FeII(L•)2][TCNQF4•−]2: A Redox-Active Double Radical Salt

Publisher: CSIRO Publishing

Date: 2019

DOI: 10.1071/CH19175

Abstract: The reaction of [FeII(L•)2][BF4]2 with LiTCNQF4 results in the formation of [FeII(L•)2][TCNQF4•−]2·2CH3CN (1) (L• is the neutral aminoxyl radical ligand 4,4-dimethyl-2,2-di(2-pyridyl)oxazolidine-N-oxide TCNQF4 is 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). Single-crystal X-ray diffraction Raman, Fourier-transform infrared (FTIR) and ultraviolet–visible spectroscopies and electrochemical studies are all consistent with the presence of a low-spin FeII ion, the neutral radical form (L•) of the ligand, and the radical anion TCNQF4•−. 1 is largely diamagnetic and the electrochemistry shows five well-resolved, diffusion-controlled, reversible one-electron processes.

Peptide Self‐Assembly into Amyloid Fibrils at Hard and Soft Interfaces—From Corona Formation to Membrane Activity

Publisher: Wiley

Date: 10-03-2023

DOI: 10.1002/MABI.202200576

Abstract: Peptides and proteins are exposed to a variety of interfaces in a physiological environment, such as cell membranes, protein nanoparticles (NPs), or viruses. These interfaces have a significant impact on the interaction, self‐assembly, and aggregation mechanisms of biomolecular systems. Peptide self‐assembly, particularly amyloid fibril formation, is associated with a wide range of functions however, there is a link with neurodegenerative diseases, such as Alzheimer's disease. This review highlights how interfaces affect peptide structure and the kinetics of aggregation leading to fibril formation. In nature, many surfaces are nanostructures, such as liposomes, viruses, or synthetic NPs. Once exposed to a biological medium, nanostructures are coated with a corona, which then determines their activity. Both accelerating and inhibiting effects on peptide self‐assembly have been observed. When amyloid peptides adsorb to a surface, they typically concentrate locally, which promotes aggregation into insoluble fibrils. Starting from a combined experimental and theoretical approach, models that allow for a better understanding of peptide self‐assembly near hard and soft matter interfaces are introduced and reviewed. Research results from recent years are presented and relationships between biological interfaces, such as membranes and viruses, and amyloid fibril formation are proposed.

Curvature model for nanoparticle size effects on peptide fibril stability and molecular dynamics simulation data

Publisher: Elsevier BV

Date: 12-2022

DOI: 10.1016/J.DIB.2022.108598

Impact of nanoparticles on amyloid peptide and protein aggregation: a review with a focus on gold nanoparticles

Publisher: Royal Society of Chemistry (RSC)

Date: 2018

DOI: 10.1039/C8NR04506B

Abstract: The accelerating and inhibiting effects of nanoparticles on amyloid peptide aggregation are discussed for varying nanoparticle and peptide properties in the context of recent studies.

Organogels Derived from Tetranitrated Crown Ethers

Publisher: American Chemical Society (ACS)

Date: 28-02-2006

DOI: 10.1021/OL060142J

Abstract: [reaction: see text] The 3,3',4'4'-tetranitrodibenzocrown ethers TNDB24C8 and TNDB30C10 form organogels with chloroalkanes at 3% w/v. Atomic force microscopy and scanning electron microscopy have been used to characterize the superstructure of the gels. Gels prepared using TNDB30C10 and CHCl(3) are more fibrous and are ordered into elongated domains attributable to exposed parts of intermingled fibers. Differential scanning calorimetry shows that the gel aids in the formation of supercooled CHCl(3) (DeltaT = 21 K, DeltaH(av) = 19.0 +/- 1.5 kJ mol(-)(1)) and that the gel liquefies at 307 K.

An SECM study on the influence of cationic, membrane-active peptides on a gold-supported self-assembled monolayer

Publisher: Elsevier BV

Date: 02-2015

DOI: 10.1016/J.ELECOM.2014.11.018

A mechanistic investigation of cell-penetrating Tat peptides with supported lipid membranes

Publisher: Elsevier BV

Date: 07-2011

DOI: 10.1016/J.BBAMEM.2011.03.002

Abstract: The multifarious Tat peptide derived from the HIV-1 virus exhibits antimicrobial activity. In this article, we use Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) to investigate the mechanisms of action of Tat (44-57) and Tat (49-57) on bacterial-mimetic 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phospho-rac-(1-glycerol) (sodium salt) (DMPG) membranes. The results reveal that both peptides disrupt DMPC/DMPG membranes via a surface-active (carpet-like) mechanism. The magnitude of this disruption is dependent on both membrane and peptide properties. Firstly, less disruption was observed on the more negatively charged membranes. Secondly, less disruption was observed for the longer and slightly more hydrophobic Tat (44-57) peptide. As a comparison, the behaviour of the two Tat peptides on mammalian-mimetic DMPC/cholesterol membranes was investigated. Consistent with the literature no membrane disruption was observed. These results suggest that both electrostatic and hydrophobic interactions, as well as peptide geometry, determine the antimicrobial activity of Tat. This should guide the development of more potent Tat antibiotics.

The Amyloid Fibril-Forming Properties of the Amphibian Antimicrobial Peptide Uperin 3.5

Publisher: Wiley

Date: 16-12-2015

DOI: 10.1002/CBIC.201500518

Abstract: The hibian skin is a vast resource for bioactive peptides, which form the basis of the animals' innate immune system. Key components of the secretions of the cutaneous glands are antimicrobial peptides (AMPs), which exert their cytotoxic effects often as a result of membrane disruption. It is becoming increasingly evident that there is a link between the mechanism of action of AMPs and amyloidogenic peptides and proteins. In this work, we demonstrate that the broad-spectrum hibian AMP uperin 3.5, which has a random-coil structure in solution but adopts an α-helical structure in membrane-like environments, forms amyloid fibrils rapidly in solution at neutral pH. These fibrils are cytotoxic to model neuronal cells in a similar fashion to those formed by the proteins implicated in neurodegenerative diseases. The addition of small quantities of 2,2,2-trifluoroethanol accelerates fibril formation by uperin 3.5, and is correlated with a structural stabilisation induced by this co-solvent. Uperin 3.5 fibril formation and the associated cellular toxicity are inhibited by the polyphenol (-)-epigallocatechin-3-gallate (EGCG). Furthermore, EGCG rapidly dissociates fully formed uperin 3.5 fibrils. Ion mobility-mass spectrometry reveals that uperin 3.5 adopts various oligomeric states in solution. Combined, these observations imply that the mechanism of membrane permeability by uperin 3.5 is related to its fibril-forming properties.

Synthesis, physical properties and X-ray crystal structure of an oxovanadium(IV) complex of the pendant-arm macrocycle 6,13-dimethyl 1,4,8,11-tetra-azacyclotetradecane-6,13-diamine

Publisher: Royal Society of Chemistry (RSC)

Date: 1990

DOI: 10.1039/DT9900002859

A new method for electrocrystallization of AgTCNQF4 and Ag2TCNQF4 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) in acetonitrile

Publisher: Springer Science and Business Media LLC

Date: 12-07-2011

DOI: 10.1007/S10008-011-1459-8

Mechanistic insights into the size-dependent effects of nanoparticles on inhibiting and accelerating amyloid fibril formation

Publisher: Elsevier BV

Date: 09-2022

DOI: 10.1016/J.JCIS.2022.04.134

Abstract: The aggregation of peptides into amyloid fibrils has been linked to ageing-related diseases, such as Alzheimer's and type 2 diabetes. Interfaces, particularly those with large nanostructured surfaces, can affect the kinetics of peptide aggregation, which ranges from complete inhibition to strong acceleration. While a number of physiochemical parameters determine interfacial effects, we focus here on the role of nanoparticle (NP) size and curvature. We used thioflavin T (ThT) fluorescence assays to demonstrate the size-dependent effects of NPs on amyloid fibril formation for the peptides Aβ

Alzheimer's Disease Therapeutics: New Approaches to an Ageing Problem

Publisher: Wiley

Date: 04-2004

DOI: 10.1080/15216540410001709211

Abstract: Abnormal proteinaceous deposits are found in the brain of patients with many different neurodegenerative diseases. In many of these diseases, the production of the deposits is probably associated with disease pathogenesis. In Alzheimer's disease (AD), the amyloid protein (A beta), is produced by the action of enzymes known as secretases, which cleave the beta-amyloid protein precursor. A beta is secreted from cells in the brain, after which it oligomerizes and is deposited in the extracellular compartment of the brain to form amyloid plaques and amyloid angiopathy. Targeting the production of A beta and its aggregation is now a key strategy in the development of novel therapeutic agents for the treatment of AD. This review examines the potential of immunization strategies, cholesterol-lowering drugs, protease inhibitors and nicotinic drugs for the treatment of AD.

Cell penetrating apidaecin peptide interactions with biomimetic phospholipid membranes

Publisher: Springer Science and Business Media LLC

Date: 04-2009

DOI: 10.1007/S10989-009-9175-2

Secondary Structure Transitions for a Family of Amyloidogenic, Antimicrobial Uperin 3 Peptides in Contact with Sodium Dodecyl Sulfate.

Publisher: Wiley

Date: 2022

DOI: 10.1002/CPLU.202100408

Abstract: Secondary structure changes are an inherent part of antimicrobial (AMP) and amyloidogenic peptide activity, especially in close proximity to membranes, and impact the peptides' function and dysfunction roles. The formation, and stability of α-helical components are regarded as essential 'intermediates' for both these functions. To illuminate the conformational transitions leading to amyloid formation we use short cationic AMPs, from an Australian toadlet, Uperoleia mjobergii, (Uperin 3 family, U3) and assess the impact on secondary structural elements in the presence of a membrane mimetic surfactant, sodium dodecyl sulfate (SDS). Specifically, Uperin 3.x, where x=4, 5, 6 wild-type peptides and position seven variants for each, R7A or K7A, were investigated using a combination of experimental and simulation approaches. In water, U3 peptides remain largely unstructured as random coils, with the addition of salts initiating structural transitions leading to assembly towards amyloid. Solution NMR data show that an unstructured U3.5 wt peptide transitions in the presence of SDS to a well-defined α-helical structure that spans nearly the entire sequence. Circular dichroism (CD) and ThT fluorescence studies show that all six U3 peptides aggregate in solution, albeit with vastly varying rates, and a dynamic equilibrium between soluble aggregates rich in either α-helices or β-sheets may exist in solution. However, the addition of SDS leads to a rapid disaggregation for all peptides and stabilisation of predominantly α-helical content in all the U3 peptides. Molecular dynamics (MD) simulations show that the adsorption of U3.5 wt/R7A peptides onto the SDS micelle is driven by Coulombic attraction between peptide cationic residues and the negatively charged sulfate head-groups on SDS. Simulating the interactions of various kinds of β-sheet dimers (of both U3.5 wt and its variant U3.5 R7A) with SDS micelles confirmed β-sheet content decreases in the dimers after their attachment to the SDS micelle. Adsorbed peptides interact favourably with the hydrophobic core of the micelle, promoting intramolecular hydrogen bonds leading to stabilisation of the α-helical structure in peptides, and resulting in a corresponding decrease in intermolecular hydrogen bonds responsible for β-sheets.

The ligand field 1A1-5T2 spin crossover with iron(II) encapsulated in hexa-amine cages

Publisher: Elsevier BV

Date: 07-1994

DOI: 10.1016/S0277-5387(00)83479-8

Organization of cytochrome P450 enzymes involved in sex steroid synthesis: Protein-protein interactions in lipid membranes

Publisher: Elsevier BV

Date: 11-2009

DOI: 10.1074/JBC.M109.006064

Mechanistic Details of the Membrane Perforation and Passive Translocation of TAT Peptides

Publisher: Wiley

Date: 30-10-2014

DOI: 10.1002/CPLU.201402209

Abstract: The trans‐activator of transcription (TAT) peptide is regarded as the “gold standard” for cell‐penetrating peptides, capable of traversing a mammalian membrane passively into the cytosolic space. This characteristic has been exploited through conjugation of TAT for applications such as drug delivery. However, the process by which TAT achieves membrane penetration remains ambiguous and unresolved. Mechanistic details of TAT peptide action are revealed herein by using three complementary methods: quartz crystal microbalance with dissipation (QCM‐D), scanning electrochemical microscopy (SECM) and atomic force microscopy (AFM). When combined, these three scales of measurement define that the membrane uptake of the TAT peptide is by trans‐membrane insertion using a “worm‐hole” pore that leads to ion permeability across the membrane layer. AFM data provided nanometre‐scale visualisation of TAT punctuation using a mammalian‐mimetic membrane bilayer. The TAT peptide does not show the same specificity towards a bacterial mimetic membrane and QCM‐D and SECM showed that the TAT peptide demonstrates a disruptive action towards these membranes. This investigation supports the energy‐independent uptake of the cationic TAT peptide and provides empirical data that clarify the mechanism by which the TAT peptide achieves its membrane activity. The novel use of these three biophysical techniques provides valuable insight into the mechanism for TAT peptide translocation, which is essential for improvements in the cellular delivery of TAT‐conjugated cargoes including therapeutic agents required to target specific intracellular locations.

The Kinetics of Amyloid Fibrillar Aggregation of Uperin 3.5 Is Directed by the Peptide’s Secondary Structure

Publisher: American Chemical Society (ACS)

Date: 06-08-2019

DOI: 10.1021/ACS.BIOCHEM.9B00536

Abstract: Many peptides aggregate into insoluble β-sheet rich amyloid fibrils. Some of these aggregation processes are linked to age-related diseases, such as Alzheimer's disease and type 2 diabetes. Here, we show that the secondary structure of the peptide uperin 3.5 directs the kinetics and mechanism of amyloid fibrillar aggregation. Uperin 3.5 variants were investigated using thioflavin T fluorescence assays, circular dichroism spectroscopy, and structure prediction methods. Our results suggest that those peptide variants with a strong propensity to form an α-helical secondary structure under physiological conditions are more likely to aggregate into amyloid fibrils than peptides in an unstructured or "random coil" conformation. This conclusion is in good agreement with the hypothesis that an α-helical transition state is required for peptide aggregation into amyloid fibrils. Specifically, uperin 3.5 variants in which charged amino acids were replaced by alanine were richer in α-helical content, leading to enhanced aggregation compared to that of wild type uperin 3.5. However, the addition of 2,2,2-trifluoroethanol as a major co-solute or membrane-mimicking phospholipid environments locked uperin 3.5 to the α-helical conformation preventing amyloid aggregation. Strategies for stabilizing peptides into their α-helical conformation could provide therapeutic approaches for overcoming peptide aggregation-related diseases. The impact of the physiological environment on peptide secondary structure could explain aggregation processes in a cellular environment.

Antimicrobial Peptides: Function, Mechanisms of Action and Role in Health and Disease

Publisher: Nova Science Publishers

Date: 2021

DOI: 10.52305/CQGC8374

Identification of TCNQF(4) redox levels using spectroscopic and electrochemical fingerprints (TCNQF(4)=2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

Publisher: Elsevier BV

Date: 2013

DOI: 10.1016/J.ICA.2012.10.019

Specific uptake and interactions of peptide nucleic acid derivatives with biomimetic membranes

Publisher: Royal Society of Chemistry (RSC)

Date: 2012

DOI: 10.1039/C2RA20462B

Two Mechanisms of Killing of Pseudomonas aeruginosa by Tobramycin Assessed at Multiple Inocula via Mechanism-Based Modeling

Publisher: American Society for Microbiology

Date: 04-2015

DOI: 10.1128/AAC.04099-14

Abstract: Bacterial resistance is among the most serious threats to human health globally, and many bacterial isolates have emerged that are resistant to all antibiotics in monotherapy. Aminoglycosides are often used in combination therapies against severe infections by multidrug-resistant bacteria. However, models quantifying different antibacterial effects of aminoglycosides are lacking. While the mode of aminoglycoside action on protein synthesis has often been studied, their disruptive action on the outer membrane of Gram-negative bacteria remains poorly characterized. Here, we developed a novel quantitative model for these two mechanisms of aminoglycoside action, phenotypic tolerance at high bacterial densities, and adaptive bacterial resistance in response to an aminoglycoside (tobramycin) against three Pseudomonas aeruginosa strains. At low-intermediate tobramycin concentrations ( mg/liter), bacterial killing due to the effect on protein synthesis was most important, whereas disruption of the outer membrane was the predominant killing mechanism at higher tobramycin concentrations (≥8 mg/liter). The extent of killing was comparable across all inocula however, the rate of bacterial killing and growth was substantially lower at the 10 8.9 CFU/ml inoculum than that at the lower inocula. At 1 to 4 mg/liter tobramycin for strain PAO1-RH, there was a 0.5- to 6-h lag time of killing that was modeled via the time to synthesize hypothetical lethal protein(s). Disruption of the outer bacterial membrane by tobramycin may be critical to enhance the target site penetration of antibiotics used in synergistic combinations with aminoglycosides and thereby combat multidrug-resistant bacteria. The two mechanisms of aminoglycoside action and the new quantitative model hold great promise to rationally design novel, synergistic aminoglycoside combination dosage regimens.

Solvent-, Cation- and Anion-Induced Structure Variations in Manganese-Based TCNQF(4) Complexes: Synthesis, Crystal Structures, Electrochemistry and Their Catalytic Properties

Publisher: Wiley

Date: 12-12-2018

DOI: 10.1002/CPLU.201700421

Abstract: The reaction of Mn(BF

Frontispiece: Polymer Nanodiscs and Their Bioanalytical Potential

Publisher: Wiley

Date: 2021

DOI: 10.1002/CHEM.202185161

Monash University

Location: Australia

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Discovery Projects - Grant ID: DP0985567

Start Date: 2009

End Date: 12-2012

Amount: $360,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0662816

Start Date: 01-2006

End Date: 12-2008

Amount: $240,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP120101066

Start Date: 2012

End Date: 12-2015

Amount: $420,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP170103477

Start Date: 02-2017

End Date: 09-2021

Amount: $304,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE100100215

Start Date: 2010

End Date: 12-2010

Amount: $350,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE210100009

Start Date: 05-2021

End Date: 05-2022

Amount: $620,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0775725

Start Date: 07-2007

End Date: 11-2008

Amount: $465,000.00

Funder: Australian Research Council

Super Science Fellowships - Grant ID: FS110200015

Start Date: 07-2011

End Date: 09-2015

Amount: $835,200.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0560685

Start Date: 2005

End Date: 06-2006

Amount: $451,000.00

Funder: Australian Research Council

Special Research Initiatives - Grant ID: SR0354474

Start Date: 01-2004

End Date: 12-2004

Amount: $30,000.00

Funder: Australian Research Council