ORCID Profile
0000-0002-6428-6760
Current Organisation
La Trobe University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Analytical Chemistry | Nanochemistry and Supramolecular Chemistry | Physical Chemistry (Incl. Structural) | Biophysics | Physical Chemistry not elsewhere classified | Nanotechnology | Nanotechnology | Physical Chemistry of Materials | Characterisation of Biological Macromolecules | Analytical Spectrometry | Medicinal and Biomolecular Chemistry | Colloid And Surface Chemistry | Classical Physics | Analytical Spectrometry | Electrochemistry | Structural Chemistry and Spectroscopy | Nanoscale Characterisation | Biochemistry and Cell Biology not elsewhere classified | Instruments And Techniques | Biological Physics | Inorganic Geochemistry Not Elsewhere Classified | Microtechnology | Microelectromechanical Systems (MEMS) | Environmental Chemistry (Incl. Atmospheric Chemistry) | Analytical Biochemistry | Nanobiotechnology | Acoustics and Acoustical Devices; Waves
ANZSRC Socio-Economic Objective (SEO)
Physical sciences | Expanding Knowledge in the Chemical Sciences | Scientific instrumentation | Prevention and treatment of pollution | Human Diagnostics | Diagnostic methods | Chemical sciences | Surgical methods and procedures | Physical and chemical conditions | Expanding Knowledge in the Physical Sciences | Scientific Instruments | Expanding Knowledge in the Biological Sciences | Diagnostics | Treatments (e.g. chemicals, antibiotics) |
Related Links
Publications
Is Indolinonic Hydroxylamine a Promising Artificial Antioxidant?
Publisher: American Chemical Society (ACS)
Date: 28-08-2019
Abstract: Indolinonic hydroxylamine (IH) is a new-generation artificial antioxidant that, due to its ability to fractionate into apolar environments, is considered for prevention against lipid peroxidation. For this reason, it is important to understand, and compare, its activity in polar and nonpolar environments. In this study, the antioxidant activity of IH has been evaluated against HO
Cholesterol Rich Domains Identified in Unilamellar Supported Biomimetic Membranes via Nano-Viscosity Measurements
Publisher: American Chemical Society (ACS)
Date: 04-05-2016
DOI: 10.1021/ACS.ANALCHEM.6B01045
Abstract: Understanding the distribution of cholesterol in phospholipid membranes is of key importance in membrane biophysics, primarily since cholesterol enriched regions, rafts, are known to play a special role in protein function. In this work, quartz crystal microbalance with dissipation (QCM)-based viscosity measurements were used to study cholesterol-induced domain formation in partially suspended single bilayer membranes. 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its mixtures with different amounts of cholesterol were studied. QCM temperature r ing experiments identified domains of different phase transition temperatures in the mixed membranes. The phase transition of DMPC shifted from 23.4 °C toward lower temperatures with increasing cholesterol content. A second, continuous but much broader, transition peak has been observed for the DMPC: cholesterol mixtures suggest that a separate cholesterol rich domain coexists with the DMPC rich domain. Importantly, the sharp DMC phase transition peak gradually diminished and eventually disappeared over 15% cholesterol content, suggesting that the cholesterol rich domain has a definite stoichiometry and once this cholesterol concentration is reached the DMPC-rich domain disappears. DSC control experiments do not show the second domain, suggesting that the phase separation only happens in nontensioned (flat) membranes.
Calculating bond dissociation energies of X−H (X=C, N, O, S) bonds of aromatic systems via density functional theory: a detailed comparison of methods
Publisher: The Royal Society
Date: 06-2022
DOI: 10.1098/RSOS.220177
Abstract: In this study, the performance of 17 different density functional theory functionals was compared for the calculation of the bond dissociation energy (BDE) values of X−H (X=C, N, O, S) bonds of aromatic compounds. The effect of the size of the basis set (expansions of 6-31(G)) was also assessed for the initial geometry and zero-point energy calculations, followed by the single-point BDE calculations with different model chemistries with the 6-311 + (3df,2p) basis set. It was found that the size of the basis set for geometry optimization has a much smaller effect on the accuracy of BDE than the choice of functional for the following single-point calculations. The M06-2X, M05-2X and M08−HX functionals yielded highly accurate BDE values compared to experimental data (with the average mean unsigned error MUE = 1.2–1.5 kcal mol −1 ), performing better than any of the other functionals. The results suggest that geometry optimization may be performed with B3LYP functional and a small basis set, whereas the M06-2X, M05-2X and M08-HX density functionals with a suitably large basis set offer the best method for calculating BDEs of ArX−H (X=C, N, O, S) bonds.
Investigation of fluid cell resonances in intermittent contact mode atomic force microscopy
Publisher: AIP Publishing
Date: 09-07-2007
DOI: 10.1063/1.2753104
Abstract: In fluid, the probe resonance curve of the atomic force microscope contains several apparent resonance peaks whose origin is not well understood. In this work, the authors focus on identifying the cause of these peaks and finding the optimal imaging conditions for acoustic intermittent contact mode in fluid environment. The authors demonstrate that the peaks are also present in the spectrum of the fluid movement and in that of the shaker piezo. These peaks may or may not coincide with the natural resonance of a probe in liquid, thus it is possible to drive the probes off-resonance. Numerical calculations show the feasibility of off-resonance imaging, but predict much higher imaging force.
Antioxidant Motifs in Flavonoids: O–H versus C–H Bond Dissociation
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
A theoretical study of the radical scavenging activity of natural stilbenes
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9RA08381B
Abstract: Oxidative stress is implicated in aging and aging-related diseases, including cancer.
Cantilever flexure, adhesive/attractive and lateral force measurements on highly-oriented pyrolytic graphite by scanning force microscopy
Publisher: Elsevier BV
Date: 07-1998
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
Oxoberberine: a promising natural antioxidant in physiological environments
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2RA01372J
Abstract: Oxoberberine (OB), a radical scavenger discovered from Artabotrys thomsonii , is expected to be effective in physiological environments.
Effect of step function-like perturbation on intermittent contact mode sensors: A response analysis
Publisher: Elsevier BV
Date: 03-2003
Time-resolved investigation of the transient surface reflection changes of subpicosecond excimer laser ablated liquids
Publisher: Springer Science and Business Media LLC
Date: 12-1999
Subtle differences in initial membrane interactions underpin the selectivity of small antimicrobial peptides
Publisher: Wiley
Date: 22-12-2015
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.
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.
Nanoscale probing of cholesterol-rich domains in single bilayer dimyristoyl-phosphocholine membranes using near-field spectroscopic imaging
Publisher: American Chemical Society (ACS)
Date: 27-10-2020
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.
Controllable hierarchical self-assembly: systematic study forming metallosupramolecular frameworks on the basis of helical beta-oligoamides
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3MH01327H
Mechanistic and Kinetic Studies of the Radical Scavenging Activity of 5-
Publisher: American Chemical Society (ACS)
Date: 14-01-2022
Abstract: 5-
Oxidation reactions catalysed by molybdenum(VI) complexes grafted on UiO‐66 metal–organic framework as an elegant nanoreactor
Publisher: Wiley
Date: 22-08-2017
DOI: 10.1002/AOC.3958
Erratum: Semiconductive polymer blends: Correlating structure with transport properties at the nanoscale (Advanced Materials (2004) 16 (385))
Publisher: Wiley
Date: 05-04-2004
Nanoscale velocity-drag force relationship in thin liquid layers measured by atomic force microscopy
Publisher: AIP Publishing
Date: 25-10-2004
DOI: 10.1063/1.1808504
Abstract: The relationship between velocity and drag force acting on a nanoprobe has been measured with an atomic force microscope (AFM). A special nanoprobe “whisker” was partially submerged in thin layers of glycerol–water mixtures and moved by using the AFM in scanning mode. The viscous drag force-caused torsion of the cantilever probe was recorded as a function of scanning speed and submersion depth. A linear drag force–velocity function was determined for cylindrical bodies with diameters of the order of 50nm. The experimental results were supported by calculations for the torsional force exerted on an AFM probe dragged through a viscous medium. The viscosity was calculated for each experiment assuming no slip conditions and was in agreement with the macroscopically determined values. With some refinements, this offers a possible means of determining viscosity in thin liquid layers.
Evaporative self-assembly assisted synthesis of polymeric nanoparticles by surface acoustic wave atomization
Publisher: IOP Publishing
Date: 04-03-2008
DOI: 10.1088/0957-4484/19/14/145301
Abstract: We demonstrate a straightforward and rapid atomization process driven by surface acoustic waves that is capable of continuously producing spherical monodispersed submicron poly-ε-caprolactone particle aggregates between 150 and 200 nm, each of which are composed of nanoparticles of 5-10 nm in diameter. The size and morphologies of these particle assemblies were determined using dynamic light scattering, atomic force microscopy and transmission electron microscopy. Through scaling theory, we show that the larger particle aggregates are formed due to capillary instabilities lified by the acoustic forcing whereas the smaller particulates that form the aggregates arise due to a nucleate templating process as a result of rapid spatially inhomogeneous solvent evaporation. Minimization of the free energy associated with the evaporative process yields a critical cluster size for a single nucleus in the order of 10 nm, which roughly corresponds with the dimensions of the sub-50 nm particulates.
Validating an artificial organelle: Studies of lipid droplet-specific proteins on adiposome platform
Publisher: Elsevier BV
Date: 08-2021
Novel Engineered Ion Channel Provides Controllable Ion Permeability for Polyelectrolyte Microcapsules Coated with a Lipid Membrane
Publisher: Wiley
Date: 08-01-2009
β3-tripeptides act as sticky ends to self-assemble into a bioscaffold
Publisher: AIP Publishing
Date: 05-2018
DOI: 10.1063/1.5020105
Abstract: Peptides comprised entirely of β3-amino acids, commonly referred to as β-foldamers, have been shown to self-assemble into a range of materials. Previously, β-foldamers have been functionalised via various side chain chemistries to introduce function to these materials without perturbation of the self-assembly motif. Here, we show that insertion of both rigid and flexible molecules into the backbone structure of the β-foldamer did not disturb the self-assembly, provided that the molecule is positioned between two β3-tripeptides. These hybrid β3-peptide flanked molecules self-assembled into a range of structures. α-Arginlyglycylaspartic acid (RGD), a commonly used cell attachment motif derived from fibronectin in the extracellular matrix, was incorporated into the peptide sequence in order to form a biomimetic scaffold that would support neuronal cell growth. The RGD-containing sequence formed the desired mesh-like scaffold but did not encourage neuronal growth, possibly due to over-stimulation with RGD. Mixing the RGD peptide with a β-foldamer without the RGD sequence produced a well-defined scaffold that successfully encouraged the growth of neurons and enabled neuronal electrical functionality. These results indicate that β3-tripeptides can form distinct self-assembly units separated by a linker and can form fibrous assemblies. The linkers within the peptide sequence can be composed of a bioactive α-peptide and tuned to provide a biocompatible scaffold.
Nanoscale resolution microchannel flow velocimetry by atomic force microscopy
Publisher: AIP Publishing
Date: 09-10-2006
DOI: 10.1063/1.2358966
Abstract: The velocity of a microchannel flow was determined by atomic force microscopy (AFM) using a 50nm wide “whisker,” which was partially submerged and scanned transverse to the flow while drag was recorded. A peaked, near parabolic, flow velocity profile was found. Particle image velocity (PIV) measurements using 70nm diameter quantum-dot-coated polystyrene spheres confirmed the shape of the AFM-measured velocity profile. AFM-based nanometer resolution velocimetry confirms that the drag-velocity relationship for the whisker remains consistent over a wide range of shear values and appears to successfully resolve submicron scale flows, which are beyond the limits of conventional PIV measurements.
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
Specific and selective peptide-membrane interactions revealed using quartz crystal microbalance
Publisher: Elsevier BV
Date: 12-2007
Formation of Alkanethiol Supported Hybrid Membranes Revisited
Publisher: Wiley
Date: 24-07-2018
Abstract: A phospholipid monolayer supported on an alkanethiol self-assembled monolayer (SAM) constitutes a supported hybrid membrane, a model of biological membranes optimized for electronic access through the underlying metal support surface. It is believed that phospholipids, when deposited from aqueous liposome suspension, spontaneously cover the alkanethiol-modified surface, owing to the reduction of surface free energy of the hydrophobic alkane surface exposed to the solution. However, the formation of the hybrid layer has to overcome significant energy barriers in rupturing the vesicle and "unzipping" the membrane leaflets hence drivers of the spontaneous hybrid membrane formation are unclear. In this work, the authors studied the efficiency of the liposome deposition method to form hybrid membranes on octanethiol and hexadecanethiol SAMs in aqueous environment. Using quartz crystal microbalance to monitor the deposition process it was found that the hybrid membrane did not form spontaneously the deposit was dominated by hemi-fused liposomes that can only be removed by applying osmotic stress. However, osmotic stress yielded a reproducible layer characterized by ≈-5Hz frequency change that is also confirmed by fluorescence microscopy imaging, irrespective of lipid concentration and the chain length of the SAMs. The frequency change is ≈20% of the frequency change expected for a tightly bound bilayer membrane, or 40% of a single leaflet, suggesting that the lipid layer is in a different conformation compared to a bilayer membrane: the acyl chains are most likely parallel to the SAM surface, likely due to strong hydrophobic interaction. Comparing these results to the literature it appears that the initial formation of hybrid membranes is inhibited by the ionic environment, while osmotic stress leads to the observed unique layer conformation.
Diamond-like carbon layer formation on graphite by excimer laser irradiation
Publisher: Springer Science and Business Media LLC
Date: 06-1998
Another look at reactions of 4-hydroxycoumarin with hydroxyl radical in the environment: deprotonation and diffusion effects
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1NJ03557F
Abstract: Quantum chemistry calculations suggest that chemical fate of the anticoagulant rodenticide 4-hydroxycoumarin in the environment is crucially dependent on deprotonation in aqueous medium.
Molybdenum (VI)‐functionalized UiO‐66 provides an efficient heterogeneous nanocatalyst in oxidation reactions
Publisher: Wiley
Date: 04-09-2019
DOI: 10.1002/AOC.5225
Anomalies in nanostructure size measurements by AFM
Publisher: American Physical Society (APS)
Date: 02-09-2005
Amino acid sequence controls the self-assembled superstructure morphology of N-acetylated tri-β3-peptides
Publisher: Walter de Gruyter GmbH
Date: 08-09-2015
Abstract: Peptides based on unnatural β 3 -amino acids offer a versatile platform for the design of self-assembling nanostructures due to the folding stability of the 14-helix and the high symmetry of the side chains inherent in this geometry. We have previously described that N-terminal acetylation (Ac-) forms a supramolecular self-assembly motif that allows β 3 -peptides to assemble head-to-tail into a helical nanorod which then further bundles into hierarchical superstructures. Here we investigate the effect of the topography of the 14-helical nanorod on lateral self-assembly. Specifically, we report on the variations in the superstructure of three isomeric peptides comprising the same three β 3 -amino acid residues: β 3 -leucine (L), β 3 -isoleucine (I) β 3 -alanine (A) to give peptides Ac-β 3 [LIA], Ac-β 3 [IAL] and Ac-β 3 [ALI]. AFM imaging shows markedly different superstructures for the three peptides. Well defined synchrotron far-infrared spectra reveal uniform geometries with a high degree of similarity between the isomeric peptides in the amide modes of the 400–650 wavenumber range. Far-IR also confirms that the C-terminal carboxyl group is free in the assemblies, thus it is solvated in the dispersant. Hence, the differences in the superstructures formed by the fibers are defined primarily by van der Waals energy minimization between the varied cross sectional morphologies of the core nanorods.
Nanoviscosity Measurements Revealing Domain Formation in Biomimetic Membranes
Publisher: American Chemical Society (ACS)
Date: 24-01-2017
DOI: 10.1021/ACS.ANALCHEM.6B04256
Abstract: Partitioning of lipid molecules in biomimetic membranes is a model system for the study of naturally occurring domains, such as rafts, in biological membranes. The existence of nanometer scale membrane domains in binary lipid mixtures has been shown with microscopy methods however, the nature of these domains has not been established unequivocally. A common notion is to ascribe domain separation to thermodynamic phase equilibria. However, characterizing thermodynamic phases of single bilayer membranes has not been possible due to their extreme dimensions: the size of the domains falls to the order of tens to hundreds of nanometers whereas the membrane thickness is only a few nanometers. Here, we present direct measurements of phase transitions in single bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipid mixtures using quartz crystal microbalance-based nanoviscosity measurements. Coexisting thermodynamic phases have been successfully identified, and a phase diagram was constructed for the single bilayer binary lipid system. It was demonstrated that domain separation only takes place in planar membranes, and thus, it is absent in liposomes and not detectable in calorimetric measurements on liposome suspensions. On the basis of energetic analysis, the main transition was identified as the breaking of van der Waals interactions between the acyl chains.
The antioxidant activity of tetrahydrofuran lignans from Anogeissus rivularis: theoretical insights into the radical scavenging activity and enzyme inhibition
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3NJ03344A
Imaging bandwidth of the tapping mode atomic force microscope probe
Publisher: American Physical Society (APS)
Date: 04-04-2006
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
Dynamical properties of the Q-controlled atomic force microscope
Publisher: AIP Publishing
Date: 11-10-2004
DOI: 10.1063/1.1785863
Abstract: In intermittent contact mode atomic force microscopy (AFM), the quality factor (Q) of the oscillating probe is believed to account for the imaging speed and sensitivity. Q control is a method to artificially modify the quality factor of the probe. Here, we present a comprehensive study of the dynamics of the Q-controlled AFM. By comparing the analytical solutions of the force equations, we prove that the Q-controlled and non-Q-controlled systems are equivalent in the absence of surface forces. We also determine the conditions for the numerical simulation. In order to study the mechanism of contrast enhancement, we simulate the normal AFM operation including the surface forces. We found that there is a maximal probe sensitivity which cannot be exceeded even with Q control. Consistently, Q control enhances sensitivity only when imaging soft s les. Finally, we show that the phase signal of the Q-controlled system is more sensitive to the changes of the s le properties than in case of non-Q-controlled AFMs.
The hydroperoxyl radical scavenging activity of sulfuretin: insights from theory
Publisher: The Royal Society
Date: 07-2021
DOI: 10.1098/RSOS.210626
Abstract: Sulfuretin (SFR), which is isolated from Rhus verniciflua , Toxicodendron vernicifluum, Dahlia, Bidens tripartite and Dipterx lacunifera , is one of the most important natural flavonoids. This compound is known to have numerous biological activities among these, the antioxidant activity has not been thoroughly studied yet. In this study, the hydroperoxyl scavenging activity of SFR was examined by using density functional theory calculations. SFR is predicted to be an excellent HOO • scavenger in water at pH = 7.40 with k overall = 4.75 × 10 7 M −1 s −1 , principally due to an increase in the activity of the anionic form following the single-electron transfer mechanism. Consistently, the activity of the neutral form is more prominent in the non-polar environment with k overall = 1.79 × 10 4 M −1 s −1 following the formal hydrogen transfer mechanism. Thus, it is predicted that SFR exhibits better HOO • antiradical activity than typical antioxidants such as resveratrol, ascorbic acid or Trolox in the lipid medium. The hydroperoxyl radical scavenging of SFR in the aqueous solution is approximately 530 times faster than that of Trolox and similar to ascorbic acid or resveratrol. This suggests that SFR is a promising radical scavenger in physiological environments.
The radical scavenging activity of 4-mercaptoimidazole: theoretical insights into the mechanism, kinetics and solvent effects
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3NJ01800H
Abstract: A regeneration cycle including the removal of O 2 ˙ − and HOO˙ radicals might increase the antioxidant activity of 4-mercaptoimidazole.
Is natural fraxin an overlooked radical scavenger?
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1RA01360B
Abstract: Fraxin (FX), a typical natural product of the coumarin family, may have multiple health benefits, but it is not an outstanding natural antioxidant.
A luminescent lipid mimetic iridium(III) N-heterocyclic carbene complex for membrane labelling
Publisher: Elsevier BV
Date: 05-2020
Proteogenomic analysis reveals exosomes are more oncogenic than ectosomes
Publisher: Impact Journals, LLC
Date: 12-04-2015
Abstract: Extracellular vesicles (EVs) include the exosomes (30-100 nm) that are produced through the endocytic pathway via the multivesicular bodies and the ectosomes (100-1000 nm) that are released through the budding of the plasma membrane. Despite the differences in the mode of biogenesis and size, reliable markers that can distinguish between exosomes and ectosomes are non-existent. Moreover, the precise functional differences between exosomes and ectosomes remains poorly characterised. Here, using label-free quantitative proteomics, we highlight proteins that could be exploited as markers to discriminate between exosomes and ectosomes. For the first time, a global proteogenomics analysis unveiled the secretion of mutant proteins that are implicated in cancer progression through tumor-derived EVs. Follow up integrated bioinformatics analysis highlighted the enrichment of oncogenic cargo in exosomes and ectosomes. Interestingly, exosomes induced significant cell proliferation and migration in recipient cells compared to ectosomes confirming the oncogenic nature of exosomes. These findings ascertain that cancer cells facilitate oncogenesis by the secretion of mutant and oncoproteins into the tumor microenvironment via exosomes and ectosomes. The integrative proteogenomics approach utilized in this study has the potential to identify disease biomarker candidates which can be later assayed in liquid biopsies obtained from cancer patients.
Electrochemiluminescence of surface bound microparticles of ruthenium complexes
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B918799P
Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides
Publisher: Wiley
Date: 11-10-2017
DOI: 10.1002/AOC.4065
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.
Time-resolved shock-wave photography above 193-nm excimer laser-ablated graphite surface
Publisher: Springer Science and Business Media LLC
Date: 12-1999
Metal organic framework-supported N -heterocyclic carbene palladium complex: A highly efficient and reusable heterogeneous catalyst for Suzuki-Miyaura C-C coupling reaction
Publisher: Elsevier BV
Date: 11-2017
Antioxidant Activity of Natural Samwirin A: Theoretical and Experimental Insights
Publisher: American Chemical Society (ACS)
Date: 04-10-2021
Comparative proteomics evaluation of plasma exosome isolation techniques and assessment of the stability of exosomes in normal human blood plasma
Publisher: Wiley
Date: 18-10-2013
Abstract: Exosomes are nanovesicles released by a variety of cells and are detected in body fluids including blood. Recent studies have highlighted the critical application of exosomes as personalized targeted drug delivery vehicles and as reservoirs of disease biomarkers. While these research applications have created significant interest and can be translated into practice, the stability of exosomes needs to be assessed and exosome isolation protocols from blood plasma need to be optimized. To optimize methods to isolate exosomes from blood plasma, we performed a comparative evaluation of three exosome isolation techniques (differential centrifugation coupled with ultracentrifugation, epithelial cell adhesion molecule immunoaffinity pull-down, and OptiPrep(TM) density gradient separation) using normal human plasma. Based on MS, Western blotting and microscopy results, we found that the OptiPrep(TM) density gradient method was superior in isolating pure exosomal populations, devoid of highly abundant plasma proteins. In addition, we assessed the stability of exosomes in plasma over 90 days under various storage conditions. Western blotting analysis using the exosomal marker, TSG101, revealed that exosomes are stable for 90 days. Interestingly, in the context of cellular uptake, the isolated exosomes were able to fuse with target cells revealing that they were indeed biologically active.
Membrane morphology effects in quartz crystal microbalance characterization of antimicrobial peptide activity
Publisher: Elsevier BV
Date: 07-2020
Theoretical Study on the Antioxidant Activity of Natural Depsidones
Publisher: American Chemical Society (ACS)
Date: 31-03-2020
Large-Scale Synthesis of Nanosilica from Silica Sand for Plant Stimulant Applications
Publisher: American Chemical Society (ACS)
Date: 02-11-2022
Study of the Mechanism and Kinetics of the Radical Scavenging Activity of 2-Mercaptoimidazole
Publisher: American Chemical Society (ACS)
Date: 02-06-2023
Formation of planar unilamellar phospholipid membranes on oxidized gold substrate
Publisher: American Vacuum Society
Date: 09-2016
DOI: 10.1116/1.4963188
Abstract: Supported planar phospholipid membranes are used in a range of biophysical measurements, typically for characterizing protein–membrane interactions. Liposome deposition is the most common method to create such membranes. The ability of liposomes to fuse into a lamellar membrane during deposition is strongly dependent on the surface chemistry some important substrate materials such as oxidized gold do not promote liposome fusion. Circumventing this determinism poses an enduring challenge to membrane biophysics. Here, the authors show that the effect of surface chemistry can be overcome by using osmotic stress. Reproducible single bilayer coverage was achieved on oxidized gold surface from liposomes of a variety of lipid compositions, as demonstrated by quartz crystal microbalance measurements and confirmed via fluorescence microscopy imaging. The continuity of the deposit was confirmed by fluorescence recovery after photobleaching. Using mixtures of di-myristoyl and di-palmitoyl lipids, it was also demonstrated that the formation of fused lamellar membranes upon osmotic stress is a sensitive function of the thermodynamic phase of the membrane.
Protocol for using artificial lipid droplets to study the binding affinity of lipid droplet-associated proteins
Publisher: Elsevier BV
Date: 03-2022
Gas-deposited WO3 nanoparticles studied by scanning force microscopy
Publisher: SPIE
Date: 25-05-2004
DOI: 10.1117/12.547356
Mechanistic and kinetic studies of the radical scavenging activity of natural abietanes: A theoretical insight
Publisher: Elsevier BV
Date: 08-2021
Phenylalanine residues act as membrane anchors in the antimicrobial action of Aurein 1.2
Publisher: American Vacuum Society
Date: 26-10-2017
DOI: 10.1116/1.4995674
Abstract: Aurein 1.2 is a small cationic antimicrobial peptide, one of the shortest peptides that can exert antimicrobial activity at low micromolar concentrations. Aurein 1.2 is a surface acting peptide, following the “carpet” mechanism of thresholded membrane disruption. It is generally assumed that the activity of such cationic α-helical membrane disrupting peptides is charge driven. Here, the authors show that instead of charge interactions, aromatic phenylalanine residues of the Aurein 1.2 sequence facilitate the membrane binding. The activity of the wild type peptide was compared to mutants in which the Phe residues were substituted, singly and in tandem, with alanine. Measurements by quartz crystal microbalance, impedance spectroscopy, and dye leakage experiments demonstrated that single residue mutants retain a much-reduced activity whereas the deletion of both Phe residues prevents membrane disruption entirely. The single residue mutants exhibited an altered mechanism of action, permeabilizing but not dissolving the target membranes. These results offer a new design rule for membrane disrupting peptides with potential pharmacological applications.
Near-field diffraction in a two-dimensional V-groove and its role in SERS
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP21750J
Abstract: Optical field distribution in micro-nano geometries of miniaturized optical devices is often significantly different from that in identical but macroscopic geometries. Plasmon effects and near-field diffraction can enhance the local field intensity, leading to enhanced cross section for light absorption and scattering, which can be utilized in substrate-enhanced spectroscopies for the detection of trace amounts of adsorbed chemicals. A specific problem is an ingenious but only empirically described way to enhance signal intensity in Raman spectroscopy by the use of a substrate patterned with gold coated micron size pyramidal pits. While Raman enhancement on nanostructured substrates is generally attributed to surface plasmons, here the micron size, and thus the sub-wavelength to near-wavelength dimensions suggest that resonant enhancement emanating from optical near-field diffraction might also play a role. To answer this question, light diffraction in a projection of the pyramidal pit: a V-groove, was modelled with a modified Neerhoff-Mur formalism suitable to calculate electromagnetic field distribution in sub-wavelength structures. Under the boundary conditions a perfect conductor screen was assumed, which excludes plasmon effects. The calculations show that interference in the cavity causes a modest resonant increase in local intensity and that near-field diffraction strongly influences the field distribution, which is explained with the electrodynamic edge effect. The magnitude of the resonant electric field on its own cannot account for the experimentally observed Raman enhancement. However, a resonant enhancement of a similar magnitude is expected for the emitted Stokes frequencies. In this case the geometry implements the conditions for the classical electromagnetic Raman enhancement, ~E(4), in a good agreement with experimental results.
The antioxidant activity of natural diterpenes: theoretical insights
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0RA02681F
Abstract: Diterpenes that were isolated from Crossopetalum gaumeri (Loes.) Lundell (Celastraceae) plants are reported to exhibit a range of biological activities, in particular as radical scavengers.
The formation of gold nanoparticles using hydroquinone as a reducing agent through a localized pH change upon addition of NaOH to a solution of HAuCl4
Publisher: Elsevier BV
Date: 11-2010
Design Principles of Peptide Based Self-Assembled Nanomaterials
Publisher: Springer International Publishing
Date: 2017
DOI: 10.1007/978-3-319-66095-0_4
Abstract: The ability to design functionalized peptide nanostructures for specific applications is tied to the ability of controlling the morphologies of the self-assembled superstructures. That, in turn, is based on a thorough understanding of the structural and environmental factors affecting self-assembly. The aim of designing self-assembling nanostructures of controlled geometries is achieved via a combination of directional and non-directional second order interactions. If the interactions are distributed in a geometrically defined way, a specific and selective supramolecular self-assembly motif is the result. In this chapter we detail the role of non-covalent interactions on the self-assembly of peptides we will also discuss different types of peptide building blocks and design rules for engineering unnatural supramolecular structures.
A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0MA00123F
Abstract: Coordination crosslinking of oligoamide nanorods yields two dimensional metallosupramolecular framework.
Analytical approaches to study domain formation in biomimetic membranes
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7AN01038A
Abstract: Novel characterization methods open new horizons in the study of membrane mixtures.
The radical scavenging activity of glycozolidol in physiological environments: a quantum chemical study
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2RA05907J
Abstract: Glycozolidol (GLD), derived from Glycosmis pentaphylla , is predicted to be a good radical scavenger in physiological environments.
Adiposome Targeting and Enzymatic Activity of Lipid Droplet-Specific Proteins
Publisher: Cold Spring Harbor Laboratory
Date: 28-04-2020
DOI: 10.1101/2020.04.27.062869
Abstract: New strategies to decode the specific protein targeting mechanism on lipid droplet (LD) are urgently needed. Using adiposome, the LD binding of perilipin 2 (PLIN2), perilipin 3 (PLIN3), and adipose triglyceride lipase (ATGL) were studied. Scatchard analysis found that the binding of PLIN2 to the adiposome surface was saturable, pointing to a specific membrane binding partner. Phosphatidylinositol (PI) was found to inhibit PLIN2 binding while it did not impede PLIN3. Structural analysis combined with mutagenesis revealed that the 73 rd glutamic acid of PLIN2 is significant for the effect of PI on the protein binding. The presence of PI significantly stimulated the activity of ATGL in vitro . The phosphorylation site mutants of ATGL were found reducing the lipase activity in the adiposome system. Our study demonstrates the utility of adiposome as a powerful, manipulatable model system for the characterization of LD binding and enzymatic activity of LD proteins in vitro .
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.
Membrane Core-Specific Antimicrobial Action of Cathelicidin LL-37 Peptide Switches Between Pore and Nanofibre Formation
Publisher: Springer Science and Business Media LLC
Date: 30-11-2016
DOI: 10.1038/SREP38184
Abstract: Membrane-disrupting antimicrobial peptides provide broad-spectrum defence against localized bacterial invasion in a range of hosts including humans. The most generally held consensus is that targeting to pathogens is based on interactions with the head groups of membrane lipids. Here we show that the action of LL-37, a human antimicrobial peptide switches the mode of action based on the structure of the alkyl chains, and not the head groups of the membrane forming lipids. We demonstrate that LL-37 exhibits two distinct interaction pathways: pore formation in bilayers of unsaturated phospholipids and membrane modulation with saturated phospholipids. Uniquely, the membrane modulation yields helical-rich fibrous peptide-lipid superstructures. Our results point at alternative design strategies for peptide antimicrobials.
Viscoelastic changes measured in partially suspended single bilayer membranes
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5SM00278H
Abstract: Non-tethered partially suspended single bilayer membranes formed on functionalized gold surface allow for the determination of phase transition temperature from viscosity change upon chain melting, measured with quartz crystal microbalance.
Raman spectroscopic and atomic force microscopic study of graphite ablation at 193 and 248 nm
Publisher: Elsevier BV
Date: 02-2000
Molecular imaging and orientational changes of antimicrobial peptides in membranes.
Publisher: Springer New York
Date: 2009
The observability of poorly bound powder-like material on hard surface by atomic force microscopy
Publisher: Elsevier BV
Date: 08-2001
Growth ofCaenorhabditis elegansin Defined Media Is Dependent on Presence of Particulate Matter
Publisher: Oxford University Press (OUP)
Date: 02-2018
Abstract: Caenorhabditis elegans are typically cultured in a monoxenic medium consisting of live bacteria. However, this introduces a secondary organism to experiments, and restricts the manipulation of the nutritional environment. Due to the intricate link between genes and environment, greater control and understanding of nutritional factors are required to push the C. elegans field into new areas. For decades, attempts to develop a chemically defined, axenic medium as an alternative for culturing C. elegans have been made. However, the mechanism by which the filter feeder C. elegans obtains nutrients from these liquid media is not known. Using a fluorescence-activated cell sorting based approach, we demonstrate growth in all past axenic C. elegans media to be dependent on the presence of previously unknown particles. This particle requirement of C. elegans led to development of liposome-based, nanoparticle culturing that allows full control of nutrients delivered to C. elegans.
Anti-inflammatory activity of synthetic and natural glucoraphanin
Publisher: National Library of Serbia
Date: 2019
Abstract: Glucoraphanin is one of the best known glucosinolates because of its health benefits. The compound is known to eliminate carcinogens in tissue and hence is frequently studied for its cancer preventative properties. In this work, the total synthesis of ?- and ?-glucoraphanin epimers was attempted. ?-Glucoraphanin potassium salt was successfully synthesized in high overall yield, whereas the ?-epimer was found to be unstable as it decomposed in the final step of the total synthesis. The anti-inflammatory activity of the synthetic glucoraphanin was determined by inhibition of the release of tumor necrosis factor alpha (TNF-?) secretion in lipopolysaccharide-stimulated THP-1 cells. It was shown that in the presence of either the synthetic or natural glucoraphanin, TNF-? secretion was significantly reduced (?52 % inhibition) at a concentration of 15 ?M.
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.
Antioxidant Activities of Monosubstituted Indolinonic Hydroxylamines: A Thermodynamic and Kinetic Study
Publisher: American Chemical Society (ACS)
Date: 25-11-2019
Abstract: Indolinonic hydroxylamine (IH) is known as a potential artificial antioxidant in apolar environments. Here, a library of 108 monosubstituted derivatives was screened in silico to identify a lead compound for increased antioxidant activity, following a strategy of shortlisting based on thermochemical and kinetic properties. It was found that the presence of substituents at the 2, 4, and 7 positions increased, while substituents in other positions decreased the BDE(O-H) values, in good correlation to the electron-donating ability of substituents. Among the studied compounds, the N and 5 amine-substituted derivatives have the lowest BDE(O-H) values (62.4-64.0 kcal mol
Modelling the mechanism and kinetics of the radical scavenging activity of iminostilbene
Publisher: Elsevier BV
Date: 03-2021
Visualization and measurement of the local absorption coefficients of single bilayer phospholipid membranes using scanning near-field optical microscopy
Publisher: The Optical Society
Date: 27-11-2019
Correction: A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0MA90046J
Abstract: Correction for ‘A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods’ by Norton G. West et al. , Mater. Adv. , 2020, 1 , 1134–1141, DOI: 10.1039/D0MA00123F.
Exploring the origin of tip-enhanced Raman scattering; Preparation of efficient TERS probes with high yield
Publisher: Wiley
Date: 02-08-2012
DOI: 10.1002/JRS.3021
Supramolecular self-assembly of N-acetyl-capped β-peptides leads to nano- to macroscale fiber formation
Publisher: Wiley
Date: 19-06-2013
In Silico Evaluation of the Radical Scavenging Mechanism of Mactanamide
Publisher: American Chemical Society (ACS)
Date: 04-09-2020
Comprehensive multidimensional study of the self-assembly properties of a three residue substituted β3 oligoamide
Publisher: Walter de Gruyter GmbH
Date: 19-10-2021
Abstract: Substituted β 3 oligoamides form a unique self-assembling system where each monomer folds into a helix containing approximately three β 3 amino acids per turn, yielding a geometrically well-defined cylindrical building block that, when N-acylated, is able to self-assemble head-to-tail into nanorods that can reach several 100 μm length. It was shown in previous works that self-assembly can be achieved with a three residue long oligoamide as well that lacks any intramolecular H-bonds, yet it crystallizes in a helix-like conformation. The self-assembly properties of these small oligoamides are however elusive, suggesting a more complex system than the self-assembly of the H-bond stabilized helical monomers. Here we focus on the self-assembly behaviour of a three residue oligoamide, Ac-β 3 [LIA] where the letters denote the side chain of the analogous α amino acid. Ac-β 3 [LIA] can yield highly inhomogeneous suspensions in water with a broad range of large fibrous structures that seem to be very stable, yet occasionally fibre growth is only observed upon heating. The small size of the monomer suggests a highly dynamic equilibrium yet all previous attempts failed to clearly identify low molecular weight species. Therefore a special methodology was employed in this study to characterize the suspensions at different size ranges: SANS that is optimal to measure the small oligomers and cross sectional diameter of the assemblies, DLS that is sensitive to the large populations and therefore the length of the superstructures, and NMR that is sensitive to monomeric and small oligomeric form, in conjunction with IR spectroscopy to probe the folding and AFM to image the morphology of the assemblies. Temperature r ing was used to perturb the system to probe the dynamicity of the self-assembly. It was found that the anomalous self-assembly behaviour of Ac-β 3 [LIA] is caused by its two stable conformations, a helix-building “horseshoe” fold and a linear conformer. The latter is exclusively found in monomeric form in solution whereas the horseshoe fold is stable in solid phase and in fibrous assemblies. Small oligomers were absent. Thus the self-assembly of Ac-β 3 [LIA] is arrested by the activation energy need of the conformation change fibre growth might be triggered by conditions that allow increased conformational freedom of the monomers. This observation may be used to develop strategies for controlled switchable self-assembly.
Local laser-assisted chemical vapor deposition of diamond
Publisher: Elsevier BV
Date: 12-2000
A brief overview of global biotechnology
Publisher: Informa UK Limited
Date: 07-02-2021
A study of protein electrochemistry on a supported membrane electrode
Publisher: Springer Science and Business Media LLC
Date: 12-04-2006
Laser assisted chemical vapour deposition of diamond microstructures
Publisher: SPIE
Date: 19-08-1998
DOI: 10.1117/12.320995
Thermodynamic and Kinetic Studies of the Radical Scavenging Behavior of Hydralazine and Dihydralazine: Theoretical Insights
Publisher: American Chemical Society (ACS)
Date: 21-04-2020
Enhanced frictive, adhesive and attractive forces imaged at etch-pit edges on highly-oriented pyrolytic graphite by scanning force microscopy
Publisher: IOP Publishing
Date: 22-02-2000
Assessment of the free radical scavenging potential of cannabidiol under physiological conditions: Theoretical and experimental investigations
Publisher: Elsevier BV
Date: 2022
Author Correction: Density functional theory study of the role of benzylic hydrogen atoms in the antioxidant properties of lignans
Publisher: Springer Science and Business Media LLC
Date: 12-03-2019
DOI: 10.1038/S41598-019-40317-Y
Abstract: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
The radical scavenging activity of abietane diterpenoids: Theoretical insights
Publisher: Elsevier BV
Date: 06-2021
Nano-viscosimetry analysis of the membrane disrupting action of the bee venom peptide melittin
Publisher: Springer Science and Business Media LLC
Date: 25-07-2019
DOI: 10.1038/S41598-019-47325-Y
Abstract: Melittin is one of the most studied α-helical cationic membrane disrupting peptides. It is the main component of bee venom, however it is considered an antimicrobial peptide for its ability to kill bacteria. Melittin is believed to act by opening large toroidal pores in the plasma membrane of the targeted cells/bacteria, although this is questioned by some authors. Little is known, however, about the molecular mechanism leading to this activity. In this study the mechanism of action of melittin was studied by dye leakage and quartz crystal microbalance fingerprinting analysis in biomimetic model membranes. The results revealed the existence of multiple stages in the membrane disrupting action with characteristic differences between different membrane types. In bacterial-mimetic (charged) lipid mixtures the viscoelastic fingerprints suggest a surface-acting mechanism, whereas in mammalian-mimetic (neutral) membranes melittin appears to penetrate the bilayer already at low concentrations. In domain-forming mixed membranes melittin shows a preference for the domain containing predominantly zwitterionic lipids. The results confirm membrane poration but are inconsistent with the insertion-to-toroidal pore pathway. Therefore hypotheses of the two membrane disrupting pathways were developed, describing the membrane disruption as either surface tension modulation leading to toroidal pore formation, or linear aggregation leading to fissure formation in the membrane.
A resonance Raman spectroscopic investigation into the effects of fixation and dehydration on heme environment of hemoglobin
Publisher: Wiley
Date: 11-05-2009
DOI: 10.1002/JRS.2317
Rapid production of biocompatible polymeric nanoparticles for functionalization via radio-frequency acoustic atomization
Publisher: IEEE
Date: 08-2007
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.
Radical Scavenging Activity of Natural Anthraquinones: a Theoretical Insight
Publisher: American Chemical Society (ACS)
Date: 13-05-2021
A thermodynamic and kinetic study of the antioxidant activity of natural hydroanthraquinones
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0RA04013D
Abstract: Novel hydroanthraquinones isolated from Talaromyces islandicus EN-501 exhibited promising antioxidant properties in preliminary studies, raising the prospect of adapting these compounds for therapeutic use in diseases caused by oxidative stress.
Substitution effects on the antiradical activity of hydralazine: a DFT analysis
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0NJ03753B
Abstract: The antioxidant activity of hydralazine derivatives in the gas-phase and in physiological environments were examined by thermodynamic and kinetic calculations.
The hydroperoxyl radical scavenging activity of natural hydroxybenzoic acids in oil and aqueous environments: Insights into the mechanism and kinetics
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.PHYTOCHEM.2022.113281
Abstract: Foods that contain hydroxybenzoic acid derivatives (HBA) include red fruits, black radish, onion, and potato peel. HBA are widely known for their anti-inflammatory, anti-cancer, and especially antioxidant capabilities however, a comprehensive study of the mechanism and kinetics of the antiradical action of these compounds has not been performed. Here, we report a study on the mechanisms and kinetics of hydroperoxyl radical scavenging activity of HBA by density functional theory (DFT) calculations. According to the results, HBA exert low HOO
In Silico Study of the Radical Scavenging Activities of Natural Indole-3-Carbinols
Publisher: American Chemical Society (ACS)
Date: 16-12-2019
Abstract: Enzymatic hydrolysis of indole glucosinolates in the human body yields the Indole-3-carbinol family of compounds (I3Cs). I3Cs are implicated in the self-healing processes of the human body and thus used as over the counter dietary supplements characterized as potential antioxidants. In this study, the antioxidant activity of natural indole-3-carbinol derivatives were investigated against the HOO
Adiposome Targeting and Enzymatic Activity of Lipid Droplet-Specific Proteins
Publisher: Elsevier BV
Date: 2020
DOI: 10.2139/SSRN.3596592
Is Usnic Acid a Promising Radical Scavenger?
Publisher: American Chemical Society (ACS)
Date: 07-07-2020
Tautomerism and antioxidant power of sulfur-benzo[h]quinoline: DFT and molecular docking studies
Publisher: Elsevier BV
Date: 10-2022
Hydroxyl Radical Scavenging of Indole-3-Carbinol: A Mechanistic and Kinetic Study
Publisher: American Chemical Society (ACS)
Date: 08-11-2019
Mechanism of Action of the Antimicrobial Peptide Caerin1.1
Publisher: Wiley
Date: 27-05-2020
Structural analysis of bioinspired nano materials with synchrotron far IR spectroscopy
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CP01355D
Abstract: Synchrotron far-infrared spectroscopy was used in conjunction with density functional theory vibrational analysis to ascertain the core structure of self-assembled fibrous superstructures formed by unnatural β 3 -tripeptides.
Spring constant of microcantilevers in fundamental and higher eigenmodes
Publisher: American Physical Society (APS)
Date: 04-11-2008
Membrane binding properties of plant defensins
Publisher: Elsevier BV
Date: 05-2023
Antiradical Activity of Lignans from Cleistanthus sumatranus: Theoretical Insights into the Mechanism, Kinetics, and Solvent Effects
Publisher: American Chemical Society (ACS)
Date: 04-10-2023
Surface energy maps of nanostructures: Atomic force microscopy and numerical simulation study
Publisher: AIP Publishing
Date: 20-05-2003
DOI: 10.1063/1.1577392
Abstract: Topography and surface energy distribution of etched graphite were examined by atomic force microscopy (AFM). AFM images show atomic monolayer deep circular holes (etch pits). At certain imaging conditions, these etch pits appear surrounded by rims. Numerical simulation of AFM images reveals that the rims are formed due to an increased surface energy zone at the edges. The vertical dimension of the rim correlates with the magnitude of the local surface energy. Such a correlation between the imaging features and the surface energy profiles can be used to demarcate local chemical constituents in a composite nanomaterial.
Thermodynamic and kinetic studies of the antiradical activity of 5-hydroxymethylfurfural: computational insights
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0NJ01567A
Abstract: The antiradical properties of 5-HMF in the gas-phase and in physiological environments were examined by thermodynamic and kinetic calculations.
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.
The hydroperoxyl and superoxide anion radical scavenging activity of anthocyanidins in physiological environments: Theoretical insights into mechanisms and kinetics
Publisher: Elsevier BV
Date: 12-2021
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.
Controls and constrains of the membrane disrupting action of Aurein 1.2
Publisher: Springer Science and Business Media LLC
Date: 17-11-2015
DOI: 10.1038/SREP16378
Abstract: Aurein 1.2 is a 13 residue antimicrobial peptide secreted by the Australian tree frog Litoria Aurea . It is a surface-acting membrane disrupting peptide that permeabilizes bacterial membranes via the carpet mechanism the molecular details of this process are mostly unknown. Here the mechanism of action of Aurein 1.2 was investigated with an emphasis on the role of membrane charge and C-terminal amidation of the peptide. Using quartz crystal microbalance (QCM) fingerprinting it was found that the membrane charge correlates with membrane affinity of the peptide, however the binding and the membrane disrupting processes are not charge driven increased membrane charge reduces the membrane disrupting activity. Coarse grain simulations revealed that phenylalanine residues act as membrane anchors. Accordingly Aurein 1.2 has the ability to bind to any membrane. Furthermore, bundling precludes membrane disruption in case of wild type peptides, while non C-terminal amidated peptides form random aggregates leading to detachment from the membrane. Hence C-terminal amidation is crucial for Aurein 1.2 action. Our results suggest that Aurein 1.2 acts via aggregation driven membrane penetration. The concomitant change in the tension of the outer leaflet imposes a spontaneous curvature on the membrane, leading to disintegration.
Phenolic Contents and Antioxidant Activity of Helicteres Hirsuta Extracts
Publisher: Bentham Science Publishers Ltd.
Date: 02-2021
DOI: 10.2174/1570178617999200728205824
Abstract: Helicteres hirsuta, which belongs to the Malvaceae family, is used in traditional medicine to treat malaria, diabetes and cervical cancer. While these uses have not been validated in clinical studies thus far, extracts from H. hirsuta exhibit confirmed antioxidant and potential anti-cancer activity that warrant critical assessment. The aim of this study was to determine the antioxidant properties of different parts of the plant H. hirsuta. The antioxidant capacities of methanol extracts of different plant parts, and specific solvent fractions thereof were determined on the basis of 2,2-diphenyl−1−picrylhydrazyl (DPPH) radical scavenging and total antioxidant activity assays. The ethyl acetate fraction from the leaf material of H. hirsuta has the most potent antioxidant activity with the lowest half maximal inhibitory concentration (IC50) value of 9.50 μg/mL, that is 4 times lower than the IC50 of curcumin. The amounts of methyl gallate and rutin dominated the extracts at 8.62 ± 0.01 and 6.76 ± 0.02 mg/g, respectively, out of a total of 21.00 ± 0.01 mg/g active phenolic fraction. The amount of methyl gallate strongly correlated with total phenolic content and total antioxidant capacity, thus this compound may be useful as a marker of antioxidant activity in common medicinal plants.
The radical scavenging activity of natural ramalin: A mechanistic and kinetic study
Publisher: Elsevier BV
Date: 2020
Calcium-dependent open/closed conformations and interfacial energy maps of reconstituted hemichannels
Publisher: Elsevier BV
Date: 03-2005
Vibrational spectroscopy study of the interaction of quinoline antimalarials with ferriprotoporphyrin IX
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3482885
Insights into the mechanisms and kinetics of the hydroperoxyl radical scavenging activity of Artepillin C
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1NJ00666E
Abstract: Through the single electron transfer mechanism, Artepillin C scavenges the hydroperoxyl radical in water approximately 572 times faster than Trolox.
Insights on the kinetics and mechanisms of the peroxyl radical scavenging capacity of caftaric acid: the important role of the acid–base equilibrium
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2NJ00377E
Abstract: Considering the acid–base equilibrium, caftaric acid has been shown to be one of the best antioxidants among phenolic acids in the aqueous physiological environment.
Novel amplitude and frequency demodulation algorithm for a virtual dynamic atomic force microscope
Publisher: IOP Publishing
Date: 10-03-2006
Semiconductive Polymer Blends: Correlating Structure with Transport Properties at the Nanoscale
Publisher: Wiley
Date: 05-03-2004
Labeling phospholipid membranes with lipid mimetic luminescent metal complexes
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.BBAMEM.2014.08.005
Abstract: Lipid-mimetic metallosurfactant based luminophores are promising candidates for labeling phospholipid membranes without altering their biophysical characteristics. The metallosurfactants studied exhibit high structural and physicochemical similarity to phospholipid molecules, designed to incorporate into the membrane structure without the need for covalent attachment to a lipid molecule. In this work, two lipid-mimetic phosphorescent metal complexes are described: [Ru(bpy)2(dn-bpy)](2+) and [Ir(ppy)2(dn-bpy)](+) where bpy is 2,2'-bipyridine, dn-bpy is 4,4'-dinonyl-2,2'-bipyridine and ppy is 2-phenylpyridine. Apart from being lipid-mimetic in size, shape and physical properties, both complexes exhibit intense photoluminescence and enhanced photostability compared with conventional organic fluorophores, allowing for prolonged observation. Moreover, the large Stokes shift and long luminescence lifetime associated with these complexes make them more suitable for spectroscopic studies. The complexes are easily incorporated into dimyristoil-phosphatidyl-choline (DMPC) liposomes by mixing in the organic solvent phase. DLS reveals the labeled membranes form liposomes of similar size to that of neat DMPC membrane. Synchrotron Small-Angle X-ray Scattering (SAXS) measurements confirmed that up to 5% of either complex could be incorporated into DMPC membranes without producing any structural changes in the membrane. Fluorescence microscopy reveals that 0.5% label content is sufficient for imaging. Atomic Force Microscopic imaging confirms that liposomes of the labeled bilayers on a mica surface can fuse into a flat lamellar membrane that is morphologically identical to neat lipid membranes. These results demonstrate the potential of such lipid-mimetic luminescent metal complexes as a new class of labels for imaging lipid membranes.
Interaction of quinoline antimalarial drugs with ferriprotoporphyrin IX, a solid state spectroscopy study
Publisher: Elsevier BV
Date: 12-2011
DOI: 10.1016/J.JINORGBIO.2011.08.005
Abstract: To investigate the nature of binding of quinoline antimalarial drugs to heme and to extract experimental evidence for this binding, the interaction of ferriprotoporphyrin IX (FP) with chloroquine and quinacrine (both of which have a similar side chain) and quinoline methanol antimalarials quinine and mefloquine has been studied using IR and NIR-Raman spectroscopy in the solid state. Attenuated total reflectance infrared spectroscopic data clearly show that heme in chloroquine-FP complex is not μ-oxo dimeric indicating that the hypothesis that chloroquine binds to FP μ-oxo dimer with a stoichiometry of 1 chloroquine:2 μ-oxo dimers is not valid in the solid state. Moreover, the first vibrational spectroscopy evidence is presented for the formation of hydrogen bonding between a propionate group of heme and the tertiary amino nitrogen of chloroquine and quinacrine. Raman spectroscopy data does not provide any evidence to support the formation of a similar salt bridge in the complexes of FP with quinine and mefloquine however, it suggests that the interaction of these drugs with FP happens through coordination of the Fe(III) center of the porphyrin to the 9-hydroxy group of the drug.
Theoretical and Experimental Studies of the Antioxidant and Antinitrosant Activity of Syringic Acid
Publisher: American Chemical Society (ACS)
Date: 05-11-2020
Real-time measurement of membrane conformational states induced by antimicrobial peptides: Balance between recovery and lysis
Publisher: Springer Science and Business Media LLC
Date: 27-06-2014
DOI: 10.1038/SREP05479
Supramolecular self-assembly of 14-helical nanorods with tunable linear and dendritic hierarchical morphologies
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4NJ01926A
Abstract: Varying the solvent offers a simple way to control superstructure polymorphism of a tri-β 3 -peptide-based supramolecular system.
Geometrically Precise Building Blocks: the Self-Assembly of β-Peptides
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.CHEMBIOL.2015.10.005
Abstract: Peptides comprised entirely of β-amino acids, or β-peptides, have attracted substantial interest over the past 25 years due to their unique structural and chemical characteristics. β-Peptides form well-defined secondary structures that exhibit different geometries compared with their α-peptide counterparts, giving rise to their foldamer classification. β-Peptide foldamers can be functionalized easily and are metabolically stable and, together with the predictable side-chain topography, have led to the design of a growing number of bioactive β-peptides with a range of biological targets. The strategic engineering of chemical and topographic properties has also led to the design of β-peptide mimics of higher-order oligomers. More recently, the ability of these peptides to self-assemble into complex structures of controlled geometries has been exploited in materials applications. The focus of this mini-review is on how the unique structural features of β-peptide assemblies have been exploited in the design of self-assembled proteomimetic bundles and nanomaterials.
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.
Co-assembly of helical β3-peptides: a self-assembled analogue of a statistical copolymer
Publisher: Walter de Gruyter GmbH
Date: 26-09-2017
Abstract: Unnatural peptide self-assembly offers the means to design hierarchical nanostructures of controlled geometries, chemical function and physical properties. N-acyl β 3 peptides, where all residues are unnatural amino acids, are able to form helical fibrous structures by a head-to-tail assembly of helical monomers, extending the helix via a three point supramolecular hydrogen bonding motif. These helical nanorods were shown to be stable under a wide range of physical conditions, offering a self-assembled analogue of polymeric fibres. Hitherto the self-assembly has only been demonstrated between identical monomers however the self-assembly motif is sequence-independent, offering the possibility of hetero-assembly of different peptide monomers. Here we present a proof of principle study of head-to-tail co-assembly of two different helical unnatural peptides Ac-β 3 [WELWEL] and Ac-β 3 [LIA], where the letters denote the β 3 analogues of natural amino acids. By atomic force microscopy imaging it was demonstrated that the homo-assembly and co-assembly of these peptides yield characteristically different structures. Synchrotron small angle X-ray scattering experiments have confirmed the presence of the fibres in the solution and the averaged diameters from modelled data correlate well to the results of AFM imaging. Hence, there is evidence of co-assembly of the fibrous superstructures given that different monomers may be used to introduce variations into chemical and physical properties, the results demonstrate a self-assembled analogue of a statistical co-polymer that can be used in designing complex functional nanomaterials.
Correlation of atomic force microscopy and Raman micro-spectroscopy to study the effects of ex vivo treatment procedures on human red blood cells
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B919245J
Abstract: The effects of fixation and dehydration on the distribution of heme-based molecules inside red blood cells and the structural integrity of the cells have been investigated using Raman mapping and AFM topographic imaging. A strong correlation was observed between the thickness of the cells as determined from AFM images and the intensity of the characteristic heme bands in the Raman maps, demonstrating that heme compounds are relatively evenly distributed inside dried and fixed cells in the majority of cases. The exception occurred when cells were dried in phosphate buffered saline, where more hemichrome appears close to the periphery of the cell despite the AFM image showing a plateau like topography. Using neat formaldehyde solution as a fixative is inadequate for a complete structural preservation and results in diffusion of hemoglobin into the surrounding area. However, a mixture of formaldehyde (3%) and glutaraldehyde (0.1%) in buffer was found to be sufficient to retain the structural integrity of cells with minimal autofluorescence. This protocol was also suitable for red blood cells infected with Plasmodium falciparum parasites, and preserved the characteristic knob-like structures on the infected red blood cell surface.
Atomic Force Microscopy of Proteins
Publisher: Wiley
Date: 19-10-2011
Coordination crosslinking of helical substituted oligoamide nanorods with Cu(II)
Publisher: Informa UK Limited
Date: 18-02-2020
The radical scavenging activity of monosubstituted iminostilbenes: Theoretical insights
Publisher: Elsevier BV
Date: 12-2021
A Potent Antioxidant Sesquiterpene, Abelsaginol, from Abelmoschus sagittifolius: Experimental and Theoretical Insights
Publisher: American Chemical Society (ACS)
Date: 07-2022
Synthesis of aromatic and indole alpha-glucosinolates
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.CARRES.2017.11.004
Abstract: Aromatic and indole glucosinolates are important members of the glucosinolate family of compounds du to their potential medicinal properties. They are known to exert antioxidant and anti-carcinogenic activity either by the natural products themselves, or their metabolic products including indole-3-carbinol and isothiocyanates. Natural glucosinolates are all β-glucosinolates however, α-glucosinolates are also promising compounds for medicinal applications and hence have to be produced synthetically for any bio-activity studies. Here we report on the successful synthesis of a series of α-glucosinolates: α-neoglucobrassicin, α-4-methoxyglucobrassicin, 2,3-dichlorophenyl-α-glucosinolate for the first time. Testing for anti-inflammatory properties of these synthetic GLs, however, did not yield the expected activity.
The alkoxy radical polymerization of N-vinylpyrrolidone in organic solvents: theoretical insight into the mechanism and kinetics
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3RA03820C
Abstract: The calculations validated the radical polymerization of NVP in organic solvents with propagation rate constants of 10 1 –10 3 M −1 s −1 .
Theoretical insights into the antiradical activity and copper-catalysed oxidative damage of mexidol in the physiological environment
Publisher: The Royal Society
Date: 2022
DOI: 10.1098/RSOS.211239
Abstract: Mexidol ( MD , 2-ethyl-6-methyl-3-hydroxypyridine) is a registered therapeutic agent for the treatment of anxiety disorders. The chemical structure suggests that MD may also act as an antioxidant. In this study, the hydroperoxyl radical scavenging activity of MD was studied to establish baseline antioxidant activity, followed by an investigation of the effect of MD on the copper-catalysed oxidative damage in biological systems, using computational methods. It was found that MD exhibits moderate radical scavenging activity against HOO • in water and pentyl ethanoate solvents following the single electron transfer and formal hydrogen transfer mechanisms, respectively. MD can chelate Cu(II), forming complexes that are much harder to reduce than free Cu(II): MD chelation completely quenches the Cu(II) reduction by ascorbic acid and suppresses the rate of reduction reaction by O 2 ⋅ − that are the main reductants of Cu(II) in biological environments. Therefore, MD exerts its anti-HO • activity primarily as an OIL-1 inhibitor.
Cell penetrating apidaecin peptide interactions with biomimetic phospholipid membranes
Publisher: Springer Science and Business Media LLC
Date: 04-2009
Organization of cytochrome P450 enzymes involved in sex steroid synthesis: Protein-protein interactions in lipid membranes
Publisher: Elsevier BV
Date: 11-2009
Self-assembled nanomaterials based on beta (β3) tetrapeptides
Publisher: IOP Publishing
Date: 24-02-2016
DOI: 10.1088/0957-4484/27/13/135606
Abstract: β(3)-amino acid based polypeptides offer a unique starting material for the design of self-assembled nanostructures such as fibres and hierarchical dendritic assemblies, due to their well-defined helical geometry in which the peptide side chains align at 120° due to the 3.0-3.1 residue pitch of the helix. In a previous work we have described the head-to-tail self-assembly of N-terminal acetylated β(3)-peptides into infinite helical nanorods that was achieved by designing a bioinspired supramolecular self-assembly motif. Here we describe the effect of consecutively more polar side chains on the self-assembly characteristics of β(3)-tetrapeptides Ac-β (3)Ala-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[ALIA]), Ac-β(3)Ser-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[SLIA]) and Ac-β (3)Lys-β (3)Leu-β(3)Ile-β (3)Glu (Ac-β(3)[KLIE]). β(3)-tetrapeptides complete 1 1/3 turns of the helix: thus in the oligomeric form the side chain positions shift 120° with each added monomer, forming a regular periodic pattern along the nanorod. Dynamic light scattering (DLS) measurements confirmed that these peptides self-assemble even in highly polar solvents such as water and DMSO, while diffusion-ordered NMR spectroscopy revealed the presence of a substantial monomeric population. Temperature dependence of the size distribution in DLS measurements suggests a dynamic equilibrium between monomers and oligomers. Solution casting produced distinct fibrillar deposits after evaporating the solvent. In the case of the apolar Ac-β(3)[ALIA] the longitudinal helix morphology gives rise to geometrically defined (∼70°) junctions between fibres, forming a mesh that opens up possibilities for applications e.g. in tissue scaffolding. The deposits of polar Ac-β(3)[SLIA] and Ac-β(3)[KLIE] exhibit fibres in regular parallel alignment over surface areas in the order of 10 μm.
Excimer laser irradiation induced formation of diamond-like carbon layer on graphite
Publisher: Elsevier BV
Date: 1999
Atomic force microscope study of excimer laser treated graphite surfaces
Publisher: SPIE
Date: 1998
DOI: 10.1117/12.320984
Interaction of small ionic species with phospholipid membranes: The role of metal coordination
Publisher: Frontiers Media SA
Date: 07-01-2019
Feruloylmonotropeins: promising natural antioxidants in Paederia scandens
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3RA00458A
Abstract: Feruloylmonotropeins (FMTs), derived from Paederia scandens , are expected to be potent radical scavengers in physiological aqueous environments.
Synthesis and evaluation of the antioxidant activity of 3-pyrroline-2-ones: experimental and theoretical insights
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2RA04640G
Abstract: Derivatives of 3-hydroxy-3-pyrroline-2-one were effectively synthesized via multicomponent reactions and exhibited potential HO˙ radical scavenging activity.
A QCM-D and SAXS Study of the Interaction of Functionalised Lyotropic Liquid Crystalline Lipid Nanoparticles with siRNA
Publisher: Wiley
Date: 03-04-2017
Abstract: Biophysical studies were undertaken to investigate the binding and release of short interfering ribonucleic acid (siRNA) from lyotropic liquid crystalline lipid nanoparticles (LNPs) by using a quartz crystal microbalance (QCM). These carriers are based on phytantriol (Phy) and the cationic lipid DOTAP (1,2-dioleoyloxy-3-(trimethylammonium)propane). The nonlamellar phase LNPs were tethered to the surface of the QCM chip for analysis based on biotin-neutravidin binding, which enabled the controlled deposition of siRNA-LNP complexes with different lipid/siRNA charge ratios on a QCM-D crystal sensor. The binding and release of biomolecules such as siRNA from LNPs was demonstrated to be reliably characterised by this technique. Essential physicochemical parameters of the cationic LNP/siRNA lipoplexes-such as particle size, lyotropic phase behaviour, cytotoxicity, gene silencing and uptake efficiency-were also assessed. The SAXS data show that when the pH was lowered to 5.5 the structure of the lipoplexes did not change, thus indicating that the acidic conditions of the endosome were not a significant factor in the release of siRNA from the cationic lipidic carriers.
Density functional theory study of the role of benzylic hydrogen atoms in the antioxidant properties of lignans
Publisher: Springer Science and Business Media LLC
Date: 17-08-2018
DOI: 10.1038/S41598-018-30860-5
Abstract: Antioxidants are a erse group of chemicals with proven health benefits and thus potential preventive medicine and therapeutic applications. While most of these compounds are natural products, determining their mechanism of radical scavenging and common motifs that contribute to antioxidant activity would allow the rational design of novel antioxidants. Here the origins of the antioxidant properties of ten natural products of the lignan family were studied in silico by calculating their thermochemical properties by using ROB3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) model chemistry. Three conditions were modelled: gas phase, ethanol and water solvents. The results allowed assigning the antioxidant activity to specific moieties and structural features of these compounds. It was found that the benzylic hydrogen atoms are the most likely to be abstracted to form radicals and hence define antioxidant properties in most of the studied compounds. The results also suggested that the most likely mechanism of HOO • radical scavenging differs by the key moiety: it is hydrogen atom transfer in case the benzylic C-H bonds, however it is proton coupled electron transfer in case of the compounds where O-H bonds are responsible for radical scavenging.
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