ORCID Profile
0000-0002-1459-9865
Current Organisation
Institut Pasteur
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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)
Structural Chemistry and Spectroscopy | Bioinorganic Chemistry | Physical Chemistry (Incl. Structural) | Central Nervous System | Free Radical Chemistry
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Neurodegenerative Disorders Related to Ageing | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Alanine-2 carbonyl is an oxygen ligand in Cu2+ coordination of Alzheimer's disease amyloid-β peptide - Relevance to N-terminally truncated forms
Publisher: American Chemical Society (ACS)
Date: 04-06-2009
DOI: 10.1021/JA903669A
Abstract: Copper interactions with the beta-amyloid peptide (Abeta) are believed to play a role in Alzheimer's disease (AD), in particular due to production of reactive oxygen species and Cu(2+)-mediated oligomerization. To understand the role that copper might play in these processes, a detailed knowledge of the fundamental Cu(2+)/Abeta interactions is essential. To date, the identity of the oxygen ligand(s) involved in Cu(2+) coordination by Abeta has remained unclear. Here, we have used site-specific (13)C and (15)N labeling in conjunction with hyperfine sublevel correlation (HYSCORE) spectroscopy to unambiguously identify the carbonyl of Alanine-2 as an oxygen ligand in one of the pH-dependent Cu(2+) coordination modes of Abeta. Polarization of the carbonyl moiety by Cu(2+) could promote amide hydrolysis and cleavage of the peptide bond between Ala2 and Glu3, providing a chemical mechanism for the generation of truncated Abeta 3-40/42 species found in AD plaques.
Ternary Cu2+ Complexes of Human Serum Albumin and Glycyl-l -histidyl-l -lysine
Publisher: American Chemical Society (ACS)
Date: 03-11-2021
DOI: 10.1021/ACS.INORGCHEM.1C03084
Abstract: Human serum albumin (HSA) and the growth factor glycyl-l-histidyl-l-lysine (GHK) bind Cu
The case for abandoning therapeutic chelation of copper ions in Alzheimer's disease
Publisher: Frontiers Media SA
Date: 02-06-2017
Systematically Studying the Effect of Fluoride on the Properties of Cyclophanes Bearing Naphthalene Diimide and Dialkoxyaryl Groups
Publisher: Wiley
Date: 12-06-2017
Abstract: Anion-π interactions between the Lewis basic anion fluoride and π-acidic naphthalene diimide was systematically studied in a series of cyclophanes in which the properties are modulated through the influence of a second, electron-rich aromatic unit. The systems and subsequently generated radical anions, upon addition of fluoride, were studied by absorption spectroscopic and EPR techniques. The results infer a modulation as a result of the nature and strength of the π-π interaction in the macrocyclic structure.
Structural Insight into Redox Dynamics of Copper Bound N-Truncated Amyloid-β Peptides from in Situ X-ray Absorption Spectroscopy
Publisher: American Chemical Society (ACS)
Date: 31-08-2018
DOI: 10.1021/ACS.INORGCHEM.8B01255
Abstract: X-ray absorption spectroscopy of Cu
Synthetic, EPR spectroscopic, magnetic and X-ray crystallographic structural studies on copper(II) complexes of the tridentate N2S donor ligand formed from 6-methyl-2-formylpyridine and S-methyldithiocarbazate (Hmpsme)
Publisher: Elsevier BV
Date: 09-2005
Prion protein cleavage fragments regulate adult neural stem cell quiescence through redox modulation of mitochondrial fission and SOD2 expression
Publisher: Springer Science and Business Media LLC
Date: 24-03-2018
Spectroscopic characterization of the molybdenum cofactor of the sulfane dehydrogenase SoxCD from paracoccus pantotrophus
Publisher: American Chemical Society (ACS)
Date: 13-12-2011
DOI: 10.1021/IC102201F
Abstract: The bacterial sulfane dehydrogenase SoxCD is a distantly related member of the sulfite oxidase (SO) enzyme family that is proposed to oxidize protein-bound sulfide (sulfane) of SoxY as part of a multienzyme mechanism of thiosulfate metabolism. This study characterized the molybdenum cofactor of SoxCD1, comprising the catalytic molybdopterin subunit SoxC and the truncated c-type cytochrome subunit SoxD1. Electron paramagnetic resonance spectroscopy of the Mo(V) intermediate generated by dithionite reduction revealed low- and high-pH species with g and A((95,97)Mo) matrices nearly identical to those of SO, indicating a similar pentacoordinate active site in SoxCD1. However, no sulfite-induced reduction to Mo(V) was detected, nor could a strongly coupled (1)H signal or a phosphate-inhibited species be generated. This indicates that the outer coordination sphere controls substrate binding in SoxCD, permitting access only to protein-bound sulfur via the C-terminal tail of SoxY.
Intermediate Cu(II)-Thiolate Species in the Reduction of Cu(II)GHK by Glutathione: A Handy Chelate for Biological Cu(II) Reduction
Publisher: American Chemical Society (ACS)
Date: 15-11-2021
Tuning Radical Species in Graphene Oxide in Aqueous Solution by Photoirradiation
Publisher: American Chemical Society (ACS)
Date: 21-03-2013
DOI: 10.1021/JP311727T
Optical imaging detects apoptosis in the brain and peripheral organs of prion-infected mice
Publisher: Oxford University Press (OUP)
Date: 02-2011
Blood vessel cell death during prion disease: Implications for disease management and infection control
Publisher: Elsevier BV
Date: 11-2014
Differential modulation of Alzheimer's disease amyloid β-peptide accumulation by diverse classes of metal ligands
Publisher: Portland Press Ltd.
Date: 12-10-2007
DOI: 10.1042/BJ20070579
Abstract: Biometals have an important role in AD (Alzheimer's disease) and metal ligands have been investigated as potential therapeutic agents for treatment of AD. In recent studies the 8HQ (8-hydroxyquinoline) derivative CQ (clioquinol) has shown promising results in animal models and small clinical trials however, the actual mode of action in vivo is still being investigated. We previously reported that CQ–metal complexes up-regulated MMP (matrix metalloprotease) activity in vitro by activating PI3K (phosphoinositide 3-kinase) and JNK (c-jun N-terminal kinase), and that the increased MMP activity resulted in enhanced degradation of secreted Aβ (amyloid β) peptide. In the present study, we have further investigated the biochemical mechanisms by which metal ligands affect Aβ metabolism. To achieve this, we measured the effects of erse metal ligands on cellular metal uptake and secreted Aβ levels in cell culture. We report that different classes of metal ligands including 8HQ and phenanthroline derivatives and the sulfur compound PDTC (pyrrolidine dithiocarbamate) elevated cellular metal levels (copper and zinc), and resulted in substantial loss of secreted Aβ. Generally, the ability to inhibit Aβ levels correlated with a higher lipid solubility of the ligands and their capacity to increase metal uptake. However, we also identified several ligands that potently inhibited Aβ levels while only inducing minimal change to cellular metal levels. Metal ligands that inhibited Aβ levels [e.g. CQ, 8HQ, NC (neocuproine), 1,10-phenanthroline and PDTC] induced metal-dependent activation of PI3K and JNK, resulting in JNK-mediated up-regulation of metalloprotease activity and subsequent loss of secreted Aβ. The findings in the present study show that erse metal ligands with high lipid solubility can elevate cellular metal levels resulting in metalloprotease-dependent inhibition of Aβ. Given that a structurally erse array of ligands was assessed, the results are consistent with the effects being due to metal transport rather than the chelating ligand interacting directly with a receptor.
Effect of exercise and pump speed modulation on invasive hemodynamics in patients with centrifugal continuous-flow left ventricular assist devices
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.HEALUN.2014.11.004
Abstract: Continuous-flow left ventricular assist devices (CF-LVADs) improve functional capacity in patients with end-stage heart failure. Pump output can be increased by increased pump speed as well as changes in loading conditions. The effect of exercise on invasive hemodynamics was studied in two study protocols. The first examined exercise at fixed pump speed (n = 8) and the second with progressive pump speed increase (n = 11). Patients underwent simultaneous right-heart catheterization, mixed venous saturation, echocardiography and mean arterial pressure monitoring. Before exercise, a r speed study was performed in all patients. Patients then undertook symptom-limited supine bicycle exercise. Upward titration of pump speed at rest (by 11.6 ± 8.6% from baseline) increased pump flow from 5.3 ± 1.0 to 6.3 ± 1.0 liters/min (18.9% increase, p < 0.001) and decreased pulmonary capillary wedge pressure (PCWP 13.6 ± 5.4 to 8.9 ± 4.1 mm Hg, p < 0.001). Exercise increased pump flow to a similar extent as pump speed change alone (to 6.2 ± 1.0 liters/min, p < 0.001), but resulted in increased right- and left-heart filling pressures (right atrial pressure [RAP]: 16.6 ± 7.5 mm Hg, p < 0.001 PCWP 24.8 ± 6.7 mm Hg, p < 0.001). Concomitant pump speed increase with exercise enhanced the pump flow increase (to 7.0 ± 1.4 liters/min, p < 0.001) in Protocol 2, but did not alleviate the increase in pre-load (RAP: 20.5 ± 8.0 mm Hg, p = 0.07 PCWP: 26.8 ± 12.7 mm Hg p = 0.47). Serum lactate and NT-proBNP levels increased significantly with exercise. Pump flow increases with up-titration of pump speed and with exercise. Although increased pump speed decreases filling pressures at rest, the benefit is not seen with exercise despite concurrent up-titration of pump speed.
α-Synuclein and β-Amyloid form a Bridged Copper Complex
Publisher: Springer Science and Business Media LLC
Date: 08-04-2015
The Prion Protein N1 and N2 Cleavage Fragments Bind to Phosphatidylserine and Phosphatidic Acid; Relevance to Stress-Protection Responses.
Publisher: Public Library of Science (PLoS)
Date: 07-08-2015
Ternary Cu(II) Complex with GHK Peptide and Cis-Urocanic Acid as a Potential Physiologically Functional Copper Chelate
Publisher: MDPI AG
Date: 27-08-2020
DOI: 10.3390/IJMS21176190
Abstract: The tripeptide NH2–Gly–His–Lys–COOH (GHK), cis-urocanic acid (cis-UCA) and Cu(II) ions are physiological constituents of the human body and they co-occur (e.g., in the skin and the plasma). While GHK is known as Cu(II)-binding molecule, we found that urocanic acid also coordinates Cu(II) ions. Furthermore, both ligands create ternary Cu(II) complex being probably physiologically functional species. Regarding the natural concentrations of the studied molecules in some human tissues, together with the affinities reported here, we conclude that the ternary complex [GHK][Cu(II)][cis-urocanic acid] may be partly responsible for biological effects of GHK and urocanic acid described in the literature.
The heterogeneous nature of Cu2+ interactions with Alzheimer's amyloid-β peptide
Publisher: American Chemical Society (ACS)
Date: 29-06-2011
DOI: 10.1021/AR200014U
Abstract: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive and memory impairment. Within the brain, senile plaques, which comprise extracellular deposits of the amyloid-β peptide (Aβ), are the most common pathological feature of AD. A high concentration of Cu(2+) is found within these plaques, which are also areas under oxidative stress. Laboratory work has shown that in vitro Aβ will react with Cu(2+) to induce peptide aggregation and the production of reactive oxygen species. As such, this interaction offers a possible explanation for two of the defining pathological features observed in the AD brain: the presence of amyloid plaques, which consist largely of insoluble Aβ aggregates, and the abundant oxidative stress therein. Researchers have accordingly put forth the "metals hypothesis" of AD, which postulates that compounds designed to inhibit Cu(2+)/Aβ interactions and redistribute Cu(2+) may offer therapeutic potential for treating AD. Characterization of the pH-dependent Cu(2+) coordination of Aβ is fundamental to understanding the neurological relevance of Cu(2+)/Aβ interactions and aiding the design of new therapeutic agents. In an effort to shed light on the problem, many experimental and theoretical techniques, using a variety of model systems, have been undertaken. The preceding decade has seen numerous conflicting spectroscopic reports concerning the nature of the Cu(2+)/Aβ coordination. As the number of studies has grown, the nature of the pH-dependent ligand environment surrounding the Cu(2+) cation has remained a point of contention. In large part, the difficulties can be attributed to inappropriate choices of the model system or to methods that are incapable of quantitatively delineating the presence and identity of multiple Cu(2+) coordination modes. Electron paramagnetic resonance (EPR) is the method of choice for studying paramagnetic metal-protein interactions. With the introduction of site-specific (15)N, (17)O, and (13)C isotopic labels and the application of advanced techniques, EPR is capable of eliminating much of the ambiguity. Recent EPR studies have produced the most definitive picture of the pH-dependent Cu(2+) coordination modes of Aβ and enabled researchers to address the inconsistencies present in the literature. In this Account, we begin by briefly introducing the evidence for a role of Cu(2+) in AD as well as the potential physiological and therapeutic implications of that role. We then outline the EPR methodology used to resolve the molecular details of the Cu(2+)/Aβ interactions. No drugs are currently available for altering the course of AD, and existing therapies only offer short-term symptomatic relief. This focused picture of the role of Cu(2+) in AD-related plaques offers welcome potential for the development of new methods to combat this devastating disease.
Determination of the metal - dithiolate fold angle in mononuclear molybdenum(V) centers by EPR spectroscopy
Publisher: American Chemical Society (ACS)
Date: 02-03-2009
DOI: 10.1021/IC802343F
Abstract: The active sites of mononuclear molybdenum-containing enzymes contain a low-symmetry Mo(V)-dithiolene intermediate whose structure can be probed using electron paramagnetic resonance (EPR). The relationship between experimental EPR spectra and the electronic and geometric structure of the active site can be difficult to establish, not least because of the low molecular symmetry. When density functional theory is used, it is possible to assess this relationship by systematically varying the geometric structure and comparing the theoretical EPR parameters with those obtained experimentally. We employed this approach to examine the relationship between the metal-dithiolate fold angle and the monoclinic spin Hamiltonian parameters (g, A, beta) of a prototypical mononuclear molybdenyl model complex. By comparing the experimental EPR parameters with these results, we show that the metal-dithiolate fold angle of the complex in solution may be obtained from the non-coincidence angle beta that transforms the principal axes of g to those of A. This will provide a useful method for probing the structure of the Mo(V) intermediate of mononuclear molybdenum enzymes, where the electronic structure of the active site is modulated by the fold angle of the dithiolate ligand (the "metal-dithiolate folding effect").
Electron paramagnetic resonance characterization of the copper-resistance protein PcoC from Escherichia coli
Publisher: Springer Science and Business Media LLC
Date: 18-04-2008
DOI: 10.1007/S00775-008-0377-4
Abstract: Continuous-wave and pulsed electron paramagnetic resonance have been applied to the study of the Cu(II) site of the copper-resistance protein PcoC from Escherichia coli and certain variant forms. Electron spin echo envelope modulation (ESEEM) experiments confirm the presence of two histidine ligands, His1 and His92, at the Cu(II) site of wild-type PcoC, consistent with the available X-ray crystallographic data for the homolog CopC (67% sequence identity) from Pseudomonas syringae pv. tomato. The variants H1F and H92F each lack one of the histidine residues close to the Cu(II) site. The ESEEM data suggest that the surviving histidine residue remains as a ligand. The nA variant features an extra alanine residue at the N terminus, which demotes the His1 ligand to position 2. At least one of the two histidine residues is bound at the Cu(II) site in this form. Simulation of the (14)N superhyperfine structure in the continuous-wave spectra confirms the presence of at least three nitrogen-based ligands at the Cu(II) sites of the wild-type, H92F and nA forms, while the H1F variant has two nitrogen ligands. The spectra of wild-type form can be fitted adequately with a 3N or a 4N model. The former is consistent with the crystal structure of the CopC homolog, where His1 acts as a bidentate ligand. The latter raises the possibility of an additional unidentified nitrogen ligand. The markedly different spectra of the H1F and nA forms compared with the wild-type and H92F proteins further highlight the integral role of the N-terminal histidine residue in the high-affinity Cu(II) site of PcoC.
Interactions of α-Factor-1, a Yeast Pheromone, and Its Analogue with Copper(II) Ions and Low-Molecular-Weight Ligands Yield Very Stable Complexes
Publisher: American Chemical Society (ACS)
Date: 08-2016
DOI: 10.1021/ACS.INORGCHEM.6B01441
Abstract: α-Factor-1 (WHWLQLKPGQPMY), a peptidic pheromone of Saccharomyces cerevisiae yeast, contains a XHX type copper(II) binding N-terminal site. Using a soluble analogue, WHWSKNR-amide, we demonstrated that the W(1)H(2)W(3) site alone binds copper(II) with a Kd value of 0.18 pM at pH 7.4 and also binds imidazole (Im) in a ternary complex (Kd of 1 mM at pH 7.4). This interaction boosts the ability of the peptide to sequester copper(II) depending on the Im concentration up to a subfemtomolar range, not available for any oligopeptidic system studied before. Therefore, α-factor-1 and other XHX-type peptides are likely copper(II) carriers in biological systems.
Biophysical investigations of the prion protein using electron paramagnetic resonance
Publisher: Humana Press
Date: 2008
DOI: 10.1007/978-1-59745-234-2_13
Abstract: The binding of paramagnetic metal ions is thought to be an essential function of the prion protein and lends itself to interrogation by electron paramagnetic resonance (EPR), which probes the local coordination environment of bound metal ions to provide details of the metal-binding affinity, stoichiometry, and the symmetry and identity of its ligating atoms. It is also capable of identifying reactive oxygen/nitrogen species and peptide-derived radicals, in addition to monitoring protein-membrane dynamics and conformation by using site-directed spin labeling. An overview of the EPR technique as applied to the prion protein is given, key results are summarized, and some future experimental avenues are outlined.
A diffusion and T2 relaxation MRI study of the ovine lumbar intervertebral disc under compression in vitro
Publisher: IOP Publishing
Date: 31-07-2004
DOI: 10.1088/0031-9155/49/16/006
Abstract: The ovine lumbar intervertebral disc is a useful model for the human lumbar disc. We present preliminary estimates of diffusion coefficients and T2 relaxation times in a pilot MRI study of the ovine lumbar intervertebral disc during uniaxial compression in vitro, and identify factors that h er the ability to accurately monitor the temporal evolution of the effective diffusion tensor at high spatial resolution.
Field-swept pulsed electron paramagnetic resonance of Cr3+-doped ZBLAN fluoride glass
Publisher: IOP Publishing
Date: 19-09-2001
Normalisation of haemodynamics in patients with end-stage heart failure with continuous-flow left ventricular assist device therapy
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.HLC.2014.04.259
Abstract: New generation continuous-flow left ventricular assist devices (LVADs) utilise centrifugal pumps. Data concerning their effect on patient haemodynamics, ventricular function and tissue perfusion is limited. We aimed to document these parameters following HeartWare centrifugal continuous-flow LVAD (HVAD) implantation and to assess the impact of post-operative right heart failure (RHF). We reviewed 53 consecutive patients (mean age 49.5 ± 14.1 yrs) with HVAD implanted in the left ventricle, at St. Vincent's Hospital, Sydney, between January 2007 and August 2012. Available paired right heart catheterisation (n=35) and echocardiography (n=39) data was reviewed to assess response of invasive haemodynamics and ventricular function to LVAD support. A total of 28 patients (53%) were implanted from interim mechanical circulatory support. Seventeen patients (32%) required short-term post-implant veno-pulmonary artery extracorporeal membrane oxygenation. At 100 ± 61 days post-implant, mean pulmonary artery pressure and mean pulmonary capillary wedge pressure decreased from 38.8 ± 7.7 to 22.9 ± 7.7 mmHg and 28.3 ± 6.4 to 13.4 ± 5.4 mmHg respectively (p<0.001). LV end diastolic diameter decreased from 71.3 ± 12.7 to 61.1 ± 13.7 mm and LV end-systolic diameter from 62.7 ± 12.3 to 53.9 ± 14.4mm (p<0.001). Aortic regurgitation remained trivial. Serum sodium increased from 133.3 ± 5.7 to 139.3 ± 2.8 mmol/L and creatinine decreased from 109.1 ± 42.5 to 74.3 ± 26.2 μmol/L (p<0.001). Across the entire cohort, the six-month survival/transplant rate was significantly lower for RHF patients (72.2%, n=18) compared to those without (96.9%, n=35, p=0.01). HVAD support improves haemodynamics, LV dimensions and renal function. Following implantation with a centrifugal continuous-flow LVAD, RHF remains a significant risk with a tendency to worse outcomes in the short to medium term.
Cavitation during the protein misfolding cyclic amplification (PMCA) method - The trigger for de novo prion generation?
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.BBRC.2015.04.048
Abstract: The protein misfolding cyclic lification (PMCA) technique has become a widely-adopted method for lifying minute amounts of the infectious conformer of the prion protein (PrP). PMCA involves repeated cycles of 20 kHz sonication and incubation, during which the infectious conformer seeds the conversion of normally folded protein by a templating interaction. Recently, it has proved possible to create an infectious PrP conformer without the need for an infectious seed, by including RNA and the phospholipid POPG as essential cofactors during PMCA. The mechanism underpinning this de novo prion formation remains unknown. In this study, we first establish by spin trapping methods that cavitation bubbles formed during PMCA provide a radical-rich environment. Using a substrate preparation comparable to that employed in studies of de novo prion formation, we demonstrate by immuno-spin trapping that PrP- and RNA-centered radicals are generated during sonication, in addition to PrP-RNA cross-links. We further show that serial PMCA produces protease-resistant PrP that is oxidatively modified. We suggest a unique confluence of structural (membrane-mimetic hydrophobic/hydrophilic bubble interface) and chemical (ROS) effects underlie the phenomenon of de novo prion formation by PMCA, and that these effects have meaningful biological counterparts of possible relevance to spontaneous prion formation in vivo.
The Cu(II) affinity of the N-terminus of human copper transporter CTR1: Comparison of human and mouse sequences
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.JINORGBIO.2018.01.011
Abstract: Copper Transporter 1 (CTR1) is a homotrimeric membrane protein providing the main route of copper transport into eukaryotic cells from the extracellular milieu. Its N-terminal extracellular domain, rich in His and Met residues, is considered responsible for directing copper into the transmembrane channel. Most of vertebrate CTR1 proteins contain the His residue in position three from N-terminus, creating a well-known Amino Terminal Cu(II)- and Ni(II)-Binding (ATCUN) site. CTR1 from humans, primates and many other species contains the Met-Asp-His (MDH) sequence, while some rodents including mouse have the Met-Asn-His (MNH) N-terminal sequence. CTR1 is thought to collect Cu(II) ions from blood copper transport proteins, including albumin, but previous reports indicated that the affinity of N-terminal peptide/domain of CTR1 is significantly lower than that of albumin, casting serious doubt on this aspect of CTR1 function. Using potentiometry and spectroscopic techniques we demonstrated that MDH-amide, a tripeptide model of human CTR1 N-terminus, binds Cu(II) with K of 1.3 × 10
Probing the quaternary structure of metal-bridged peptide oligomers
Publisher: Elsevier BV
Date: 05-2016
DOI: 10.1016/J.JINORGBIO.2016.01.012
Abstract: The oligomerisation of many proteins and peptides is known to be influenced by the binding of transition metal ions such as alent copper. To investigate the oligomeric state of model peptides related to the N-terminus of α-synuclein (αSyn) in the presence of Cu(II), electron paramagnetic resonance (EPR) spectroscopy and isotopic labelling were recently used to conclude that Cu(II) occupies N-terminal bridging positions within closed-chain αSyn dimers and trimers with a Cu eptide stoichiometry of 1:1. Herein, a statistical correction is identified and the consequences are evaluated. The analysis reveals that αSyn forms Cu-bridged antiparallel dimers and closed-chain trimers that coexist with Cu(II)-bound monomers (including a "macrochelate") and, depending on metal stoichiometry and protein environment, with open-chain Cu-bridged oligomers and heterodimers. The results demonstrate that the Cu(II) ion can be exploited as a probe of protein quaternary structure, with the potential to delineate heterogeneous oligomeric populations.
Chelator PBT2 Forms a Ternary Cu2+ Complex with β-Amyloid That Has High Stability but Low Specificity
Publisher: MDPI AG
Date: 25-05-2023
DOI: 10.3390/IJMS24119267
Abstract: The metal chelator PBT2 (5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline) acts as a terdentate ligand capable of forming binary and ternary Cu2+ complexes. It was clinically trialed as an Alzheimer’s disease (AD) therapy but failed to progress beyond phase II. The β-amyloid (Aβ) peptide associated with AD was recently concluded to form a unique Cu(Aβ) complex that is inaccessible to PBT2. Herein, it is shown that the species ascribed to this binary Cu(Aβ) complex in fact corresponds to ternary Cu(PBT2)NImAβ complexes formed by the anchoring of Cu(PBT2) on imine nitrogen (NIm) donors of His side chains. The primary site of ternary complex formation is His6, with a conditional stepwise formation constant at pH 7.4 (Kc [M−1]) of logKc = 6.4 ± 0.1, and a second site is supplied by His13 or His14 (logKc = 4.4 ± 0.1). The stability of Cu(PBT2)NImH13/14 is comparable with that of the simplest Cu(PBT2)NIm complexes involving the NIm coordination of free imidazole (logKc = 4.22 ± 0.09) and histamine (logKc = 4.00 ± 0.05). The 100-fold larger formation constant for Cu(PBT2)NImH6 indicates that outer-sphere ligand–peptide interactions strongly stabilize its structure. Despite the relatively high stability of Cu(PBT2)NImH6, PBT2 is a promiscuous chelator capable of forming a ternary Cu(PBT2)NIm complex with any ligand containing an NIm donor. These ligands include histamine, L-His, and ubiquitous His side chains of peptides and proteins in the extracellular milieu, whose combined effect should outweigh that of a single Cu(PBT2)NImH6 complex regardless of its stability. We therefore conclude that PBT2 is capable of accessing Cu(Aβ) complexes with high stability but low specificity. The results have implications for future AD therapeutic strategies and understanding the role of PBT2 in the bulk transport of transition metal ions. Given the repurposing of PBT2 as a drug for breaking antibiotic resistance, ternary Cu(PBT2)NIm and analogous Zn(PBT2)NIm complexes may be relevant to its antimicrobial properties.
Alzheimer's Aβ peptides with disease-associated NTerminal modifications: Influence of isomerisation, truncation and mutation on Cu2+ coordination
Publisher: Public Library of Science (PLoS)
Date: 30-12-2010
Oligopeptides Generated by Neprilysin Degradation of β-Amyloid Have the Highest Cu(II) Affinity in the Whole Aβ Family
Publisher: American Chemical Society (ACS)
Date: 24-12-2018
DOI: 10.1021/ACS.INORGCHEM.8B03051
Abstract: The catabolism of β-amyloid (Aβ) is carried out by numerous endopeptidases including neprilysin, which hydrolyzes peptide bonds preceding positions 4, 10, and 12 to yield Aβ
Copper complexes of a novel non-innocent quadridentate ligand
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CC16658E
Abstract: Quadridentate ligand H(2)L binds Cu(I) to form salt [Cu(I)(H(2)L)]BF(4) which undergoes aerial oxidation in solution with isolation of the diamagnetic salt [Cu(II)L˙(-)]BF(4) where π-radical anion L˙(-) is the (1e(-), 2H(+)) oxidation product of H(2)L.
Near-Infrared Fluorescence Imaging of Apoptotic Neuronal Cell Death in a Live Animal Model of Prion Disease
Publisher: American Chemical Society (ACS)
Date: 30-09-2010
DOI: 10.1021/CN100068X
Polymethylmethacrylate bone cements and additives: A review of the literature
Publisher: Baishideng Publishing Group Inc.
Date: 2013
DOI: 10.5312/WJO.V4.I2.67
The N terminus of α-synuclein forms CuII-bridged oligomers
Publisher: Wiley
Date: 10-03-2015
Abstract: The oligomerization of α-synuclein (αSyn) is one of the defining features of Parkinson's disease. Binding of alent copper to the N terminus of αSyn has been implicated in both its function and dysfunction. Herein, the molecular details of the Cu(II) /αSyn binding interface have been revealed using a library of synthetic 56-residue αSyn peptides containing site-specific isotopic labels. Using electron paramagnetic resonance spectroscopy, αSyn is shown to coordinate Cu(II) with high affinity via two pH-dependent coordination modes between pH 6.5-8.5. Most remarkably, the data demonstrate that the dominant mode is associated with binding to oligomers (antiparallel dimers and/or cyclic trimers) in which Cu(II) ions occupy intermolecular bridging sites. The findings provide a molecular link between Cu(II) -bound αSyn and its associated quaternary oligomeric structure.
Dominant roles of the polybasic proline motif and copper in the PrP23-89-mediated stress protection response
Publisher: The Company of Biologists
Date: 15-05-2009
DOI: 10.1242/JCS.043604
Abstract: Beta-cleavage of the neurodegenerative disease-associated prion protein (PrP) protects cells from death induced by oxidative insults. The beta-cleavage event produces two fragments, designated N2 and C2. We investigated the role of the N2 fragment (residues 23-89) in cellular stress response, determining mechanisms involved and regions important for this reaction. The N2 fragment differentially modulated the reactive oxygen species (ROS) response induced by serum deprivation, with amelioration when copper bound. Amino acid residues 23-50 alone mediated a ROS reduction response. PrP23-50 ROS reduction was not due to copper binding or direct antioxidant activity, but was instead mediated through proteoglycan binding partners localised in or interacting with cholesterol-rich membrane domains. Furthermore, mutational analyses of both PrP23-50 and N2 showed that their protective capacity requires the sterically constraining double proline motif within the N-terminal polybasic region. Our findings show that N2 is a biologically active fragment that is able to modulate stress-induced intracellular ROS through interaction of its structurally defined N-terminal polybasic region with cell-surface proteoglycans.
The Sub-picomolar Cu
Publisher: Wiley
Date: 29-10-2020
Abstract: The apparent affinity of human serum albumin (HSA) for alent copper has long been the subject of great interest, due to its presumed role as the major Cu
Superhyperfine interactions in inhomogeneously broadened paramagnetic centers observed via a hole-burned free induction decay
Publisher: AIP Publishing
Date: 30-01-2003
DOI: 10.1063/1.1535425
Abstract: Superhyperfine interactions in inhomogeneously broadened paramagnetic centers are observed using a single high-turn-angle microwave pulse. The free induction signal that follows the hole-burning pulse exhibits oscillations that are distinct from the oscillatory free induction decay observable in some inhomogeneously broadened systems. It contains frequencies characteristic of the superhyperfine splittings, together with a zero frequency component. Experimental ex les of the effect in both orientationally disordered (powdered) and structurally disordered (glassy) systems are presented and compared with the conceptually similar Fourier transform electron paramagnetic resonance detected nuclear magnetic resonance experiment, together with numerical simulations.
Cu2+ Coordination of Covalently Cross-linked β-Amyloid Dimers
Publisher: Springer Science and Business Media LLC
Date: 23-04-2013
A novel method of blood pressure measurement in patients with continuous-flow left ventricular assist devices
Publisher: Elsevier BV
Date: 11-2014
The prion protein regulates beta-amyloid-mediated self-renewal of neural stem cells in vitro
Publisher: Springer Science and Business Media LLC
Date: 11-04-2015
A Functional Role for Aβ in Metal Homeostasis? N-Truncation and High-Affinity Copper Binding
Publisher: Wiley
Date: 14-07-2015
Abstract: Accumulation of the β-amyloid (Aβ) peptide in extracellular senile plaques rich in copper and zinc is a defining pathological feature of Alzheimer's disease (AD). The Aβ1-x (x=16/28/40/42) peptides have been the primary focus of Cu(II) binding studies for more than 15 years however, the N-truncated Aβ4-42 peptide is a major Aβ isoform detected in both healthy and diseased brains, and it contains a novel N-terminal FRH sequence. Proteins with His at the third position are known to bind Cu(II) avidly, with conditional log K values at pH 7.4 in the range of 11.0-14.6, which is much higher than that determined for Aβ1-x peptides. By using Aβ4-16 as a model, it was demonstrated that its FRH sequence stoichiometrically binds Cu(II) with a conditional Kd value of 3×10(-14) M at pH 7.4, and that both Aβ4-16 and Aβ4-42 possess negligible redox activity. Combined with the predominance of Aβ4-42 in the brain, our results suggest a physiological role for this isoform in metal homeostasis within the central nervous system.
Mixed ligand Cu2+ complexes of a model therapeutic with Alzheimer's amyloid-β peptide and monoamine neurotransmitters
Publisher: American Chemical Society (ACS)
Date: 28-03-2013
DOI: 10.1021/IC302289R
Abstract: 8-Hydroxyquinolines (8HQ) have found widespread application in chemistry and biology due to their ability to complex a range of transition metal ions. The family of 2-substituted 8HQs has been proposed for use in the treatment of Alzheimer's disease (AD). Most notably, the therapeutic PBT2 (Prana Biotechnology Ltd.) has been shown to act as an efficient metal chaperone, disaggregate metal-enriched amyloid plaques comprised of the Aβ peptide, inhibit Cu/Aβ redox chemistry, and reverse the AD phenotype in transgenic animal models. Yet surprisingly little is known about the molecular interactions at play. In this study, we show that the homologous ligand 2-[(dimethylamino)methyl]-8-hydroxyquinoline (HL) forms a CuL complex with a conditional (apparent) dissociation constant of 0.33 nM at pH 6.9 and is capable of forming ternary Cu(2+) complexes with neurotransmitters including histamine (HA), glutamic acid (Glu), and glycine (Gly), with glutathione disulfide (GSSG), and with histidine (His) side chains of proteins and peptides including the Aβ peptide. Our findings suggest a molecular basis for the strong metal chaperone activity of PBT2, its ability to attenuate Cu(2+)/Aβ interactions, and its potential to promote neuroprotective and neuroregenerative effects.
A new heterobinuclear FeIIICuII complex with a single terminal FeIII–O(phenolate) bond. Relevance to purple acid phosphatases and nucleases
Publisher: Springer Science and Business Media LLC
Date: 21-04-2005
DOI: 10.1007/S00775-005-0635-7
Abstract: A novel heterobinuclear mixed valence complex [Fe(III)Cu(II)(BPBPMP)(OAc)(2)]ClO(4), 1, with the unsymmetrical N(5)O(2) donor ligand 2-bis[{(2-pyridylmethyl)aminomethyl}-6-{(2-hydroxybenzyl)(2-pyridylmethyl)}aminomethyl]-4-methylphenol (H(2)BPBPMP) has been synthesized and characterized. A combination of data from mass spectrometry, potentiometric titrations, X-ray absorption and electron paramagnetic resonance spectroscopy, as well as kinetics measurements indicates that in ethanol/water solutions an [Fe(III)-(mu)OH-Cu(II)OH(2)](+) species is generated which is the likely catalyst for 2,4-bis(dinitrophenyl)phosphate and DNA hydrolysis. Insofar as the data are consistent with the presence of an Fe(III)-bound hydroxide acting as a nucleophile during catalysis, 1 presents a suitable mimic for the hydrolytic enzyme purple acid phosphatase. Notably, 1 is significantly more reactive than its isostructural homologues with different metal composition (Fe(III)M(II), where M(II) is Zn(II), Mn(II), Ni(II), or Fe(II)). Of particular interest is the observation that cleavage of double-stranded plasmid DNA occurs even at very low concentrations of 1 (2.5 microM), under physiological conditions (optimum pH of 7.0), with a rate enhancement of 2.7 x 10(7) over the uncatalyzed reaction. Thus, 1 is one of the most effective model complexes to date, mimicking the function of nucleases.
A 2-Substituted 8-Hydroxyquinoline Stimulates Neural Stem Cell Proliferation by Modulating ROS Signalling
Publisher: Springer Science and Business Media LLC
Date: 21-06-2016
DOI: 10.1007/S12013-016-0747-4
Abstract: Eight-hydroxyquinolines (8HQs) are a class of compounds that have been identified as potential therapeutics for a number of neurodegenerative diseases. Understanding the influence of structural modifications to the 8HQ scaffold on cellular behaviour will aid the identification of compounds that might be effective in treating dementias. In this study, we describe the action of 2-[(dimethylamino)methyl]-8-hydroxyquinoline (DMAMQ) on adult murine neural stem cells (NSCs) cultured in vitro. Treatment of NSCs with DMAMQ resulted in enhanced self-renewal and increased neurite outgrowth. Concurrent with the positive growth effects was an increase in intracellular reactive oxygen species, with the growth being inhibited by inactivation of the NADPH oxidase (Nox) enzyme family. Our results indicate that DMAMQ can stimulate neurogenesis via the Nox signalling pathway, which may provide therapeutic benefit in treating dementias of various types by replenishing neurones using the brain's own reserves. The narrow concentration range over which these effects were observed, however, suggests that there may exist only a small therapeutic window for neuro-regenerative applications.
The Unusual Magnetic Resonance Properties of Trigonal Prismatic Tc and Re Complexes
Publisher: Springer Science and Business Media LLC
Date: 05-05-2011
Copper Exchange and Redox Activity of a Prototypical 8-Hydroxyquinoline: Implications for Therapeutic Chelation
Publisher: American Chemical Society (ACS)
Date: 13-07-2016
DOI: 10.1021/ACS.INORGCHEM.6B00832
Abstract: The N-truncated β-amyloid (Aβ) isoform Aβ4-x is known to bind Cu(2+) via a redox-silent ATCUN motif with a conditional Kd = 30 fM at pH 7.4. This study characterizes the Cu(2+) interactions and redox activity of Aβx-16 (x = 1, 4) and 2-[(dimethylamino)-methyl-8-hydroxyquinoline, a terdentate 8-hydroxyquinoline (8HQ) with a conditional Kd(CuL) = 35 pM at pH 7.4. Metal transfer between Cu(Aβ1-16), CuL, CuL2, and ternary CuL(NIm(Aβ)) was rapid, while the corresponding equilibrium between L and Aβ4-16 occurred slowly via a metastable CuL(NIm(Aβ)) intermediate. Both CuL and CuL2 were redox-silent in the presence of ascorbate, but a CuL(NIm) complex can generate reactive oxygen species. Because the NIm(Aβ) ligand will be readily exchangeable with NIm ligands of ubiquitous protein His side chains in vivo, this class of 8HQ ligand could transfer Cu(2+) from inert Cu(Aβ4-x) to redox-active CuL(NIm). These findings have implications for the use of terdentate 8HQs as therapeutic chelators to treat neurodegenerative disease.
Role of Nox inhibitors plumbagin, ML090 and gp91ds-tat peptide on homocysteine thiolactone induced blood vessel dysfunction.
Publisher: Wiley
Date: 28-07-2015
Abstract: Antioxidants have not reduced the burden of cardiovascular disease, and current evidence suggests a beneficial role of oxidative stress, via NADPH oxidase (Nox) upregulation, in endothelial function. Homocysteine thiolactone (HcyT) induces blood vessel dysfunction and this correlates with increased vascular oxidative stress. This study aimed to determine if pharmacological inhibition of Nox could impair HcyT induced blood vessel dysfunction. Abdominal aorta were excised from New Zealand White rabbits (n = 6), cut into rings and sequentially mounted in organ baths. Rings were preincubated with 0.55 μmol/L homocysteine thiolactone for 1 h, or combinations of putative Nox inhibitors (plumbagin for Nox4, gp91ds-tat for Nox2, and ML090 for Nox1), 30 min prior to the addition of HcyT, followed by a dose response curve to acetylcholine on phenylephrine preconstricted rings. Plumbagin, ML090 + gp91ds-tat and HcyT reduced responses to acetylcholine, and Plumbagin + Hcyt caused constriction to acetylcholine, which was normalised to plumbagin by ML090. Plumbagin + ML090 or plumbagin + gp91ds-tat completely impaired the effect of acetylcholine. ML090 inhibited the effect of HcyT on reduced response to acetylcholine, whereas gp91ds-tat had no effect. This study concludes that inhibition of Nox1 prevents, whereas inhibition of Nox4 worsens, acetylcholine induced blood vessel relaxation caused by HcyT, while Nox2 inhibition has no effect. However combinations of Nox inhibitors worsen acetylcholine induced blood vessel relaxation. These results suggest that there is cross-talk between Nox isoforms during physiological and pathophysiological processes.
Identification of the Binding Site of Apical Membrane Antigen 1 (AMA1) Inhibitors Using a Paramagnetic Probe.
Publisher: Wiley
Date: 13-02-2019
Abstract: Apical membrane antigen 1 (AMA1) is essential for the invasion of host cells by malaria parasites. Several small-molecule ligands have been shown to bind to a conserved hydrophobic cleft in Plasmodium falciparum AMA1. However, a lack of detailed structural information on the binding pose of these molecules has hindered their further optimisation as inhibitors. We have developed a spin-labelled peptide based on RON2, the native binding partner of AMA1, to probe the binding sites of compounds on PfAMA1. The crystal structure of this peptide bound to PfAMA1 shows that it binds at one end of the hydrophobic groove, leaving much of the binding site unoccupied and allowing fragment hits to bind without interference. In paramagnetic relaxation enhancement (PRE)-based NMR screening, the
The N-terminal 14-mer model peptide of human Ctr1 can collect Cu(ii ) from albumin. Implications for copper uptake by Ctr1
Publisher: Oxford University Press (OUP)
Date: 2018
DOI: 10.1039/C8MT00274F
Abstract: The superior Cu( ii ) affinity of human copper transporter 1 (hCtr1) drives copper acquisition from human serum albumin (HSA).
On the ability of CuAβ1-x peptides to form ternary complexes: Neurotransmitter glutamate is a competitor while not a ternary partner
Publisher: Elsevier BV
Date: 05-2016
DOI: 10.1016/J.JINORGBIO.2016.02.035
Abstract: In the light of conflicting reports on the ability of copper(II) complexes of amyloid beta (Aβ) peptides to form ternary complexes with small molecules co-present in the biological milieu, we performed a study of coordination equilibria in the system containing Cu(II) ions, the Aβ1-16 peptide, glutamic acid and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid, HEPES) buffer. Using potentiometry, isothermal titration calorimetry (ITC), UV-visible spectroscopy and EPR, we concluded that glutamic acid was not able to form such a ternary complex, but can efficiently compete for the Cu(II) ion with the Aβ peptide at Glu concentrations relevant for the synaptic cleft. We also found that the literature constants for Cu(II) complexes with Glu were overestimated, but this effect was partially compensated by the formation of a ternary Cu(Glu)(HEPES) complex. Our results indicate that small molecules co-present with Cu(II) ions and Aβ peptides in the synaptic cleft are not very likely to enhance Cu(II)/Aβ interactions, but instead should be considered as a Cu(II) buffering system that may help prevent these interactions and participate in Cu(II) clearance from the synaptic cleft.
In vivo-near infrared imaging of neurodegeneration
Publisher: Springer New York
Date: 2017
DOI: 10.1007/978-1-4939-7244-9_17
Abstract: In vivo near-infrared (NIR) imaging of molecular processes at the preclinical stage promises to provide more valuable mechanistic information about pathological pathways involved in neurodegeneration. NIR imaging has the potential to improve in vivo therapeutic screening protocols by enabling noninvasive monitoring of presymptomatic responses to treatment. We have developed new NIR fluorescent contrast agents conjugated to markers of cell death, and using these agents we have identified molecular pathways associated with prion-induced neurodegeneration and determined the optimal window for meaningful therapeutic intervention in prion disease. This chapter provides a description of the synthesis and purification of our NIR cell Death (NIRD) contrast agent and the application of in vivo NIRD (iNIRD) imaging to a prion model of neurodegeneration.
Redox Activity and Two-Step Valence Tautomerism in a Family of Dinuclear Cobalt Complexes with a Spiroconjugated Bis(dioxolene) Ligand
Publisher: American Chemical Society (ACS)
Date: 24-05-2013
DOI: 10.1021/JA4021155
Abstract: A family of dinuclear cobalt complexes with bridging bis(dioxolene) ligands derived from 3,3,3',3'-tetramethyl-1,1'-spirobis(indane-5,5',6,6'-tetrol) (spiroH4) and ancillary ligands based on tris(2-pyridylmethyl)amine (tpa) has been synthesized and characterized. The bis(dioxolene) bridging ligand is redox-active and accessible in the (spiro(cat-cat))(4-), (spiro(SQ-cat))(3-), and (spiro(SQ-SQ))(2-) forms, (cat = catecholate, SQ = semiquinonate). Variation of the ancillary ligand (Mentpa n = 0-3) by successive methylation of the 6-position of the pyridine rings influences the redox state of the complex, governing the distribution of electrons between the cobalt centers and the bridging ligands. Pure s les of salts of the complexes [Co2(spiro)(tpa)2](2+) (1), [Co2(spiro)(Metpa)2](2+) (2), [Co2(spiro)(Me2tpa)2](2+) (3), [Co2(spiro)(Me3tpa)2](2+) (4), [Co2(spiro)(tpa)2](3+) (5), and [Co2(spiro)(tpa)2](4+) (6) have been isolated, and 1, 4, and 6 have been characterized by single crystal X-ray diffraction. Studies in the solid and solution states using multiple techniques reveal temperature invariant redox states for 1, 2, and 4-6 and provide clear evidence for four different charge distributions: 1 and 2 are Co(III)-(spiro(cat-cat))-Co(III), 4 is Co(II)-(spiro(SQ-SQ))-Co(II), 5 is Co(III)-(spiro(SQ-cat))-Co(III), and 6 is Co(III)-(spiro(SQ-SQ))-Co(III). Of the six complexes, only 3 shows evidence of temperature dependence of the charge distribution, displaying a rare thermally induced two-step valence tautomeric transition from the Co(III)-(spiro(cat-cat))-Co(III) form to Co(II)-(spiro(SQ-cat))-Co(III) and then to Co(II)-(spiro(SQ-SQ))-Co(II) in both solid and solution states. This is the first time a two-step valence tautomeric (VT) transition has been observed in solution. Partial photoinduction of the VT transition is also possible in the solid. Magnetic and spectroscopic studies of 5 and 6 reveal that spiroconjugation of the bis(dioxolene) ligand allows electronic interaction across the spiro bridge, suggesting that thermally activated vibronic coupling between the two cobalt-dioxolene moieties plays a key role in the two-step transition evident for 3.
Electron paramagnetic resonance microscopy using spins in diamond under ambient conditions
Publisher: Springer Science and Business Media LLC
Date: 06-09-2017
Cu2+ binding modes of recombinant α-synuclein - Insights from EPR spectroscopy
Publisher: American Chemical Society (ACS)
Date: 22-05-2008
DOI: 10.1021/JA800708X
Abstract: The interaction of the small (140 amino acid) protein, alpha-synuclein (alphaS), with Cu(2+) has been proposed to play a role in Parkinson's disease (PD). While some insight from truncated model complexes has been gained, the nature of the corresponding Cu(2+) binding modes in the full length protein remains comparatively less well characterized. This work examined the Cu(2+) binding of recombinant human alphaS using Electron Paramagnetic Resonance (EPR) spectroscopy. Wild type (wt) alphaS was shown to bind stoichiometric Cu(2+) via two N-terminal binding modes at physiological pH. An H50N mutation isolated one binding mode, whose g parallel, A parallel, and metal-ligand hyperfine parameters correlated well with a {NH2, N(-), beta-COO(-), H2O} mode previously identified in truncated model fragments. Electron spin-echo envelope modulation (ESEEM) studies of wt alphaS confirmed the second binding mode at pH 7.4 involved coordination of His50 and its g parallel and A parallel parameters correlated with either {NH2, N(-), beta-COO(-), N(Im)} or {N(Im), 2 N(-)} coordination observed in alphaS fragments. At pH 5.0, His50-anchored Cu(2+) binding was greatly diminished, while {NH2, N(-), beta-COO(-), H2O} binding persisted in conjunction with another two binding modes. Metal-ligand hyperfine interactions from one of these indicated a 1N3O coordination sphere, which was ascribed to a {NH2, CO} binding mode. The other was characterized by a spectrum similar to that previously observed for diethylpyrocarbonate-treated alphaS and was attributed to C-terminal binding centered on Asp121. In total, four Cu(2+) binding modes were identified within pH 5.0-7.4, providing a more comprehensive picture of the Cu(2+) binding properties of recombinant alphaS.
Neutron reflectometry studies define prion protein N-terminal peptide membrane binding
Publisher: Elsevier BV
Date: 11-2014
Theoretical calculation of the magnetic resonance parameters of trigonal-prismatic tris(o -aminobenzenethiol)technetium and -rhenium complexes
Publisher: American Chemical Society (ACS)
Date: 25-06-2010
DOI: 10.1021/IC1009175
Abstract: Spin Hamiltonian parameters for the neutral trigonal-prismatic Tc(abt)(3) and Re(abt)(3) chelates (abt = o-aminobenzenethiol) are calculated using relativistic density functional theory at the all-electron level. The small magnitude of the calculated g shifts and metal hyperfine interactions is in excellent agreement with previous experimental predictions based upon a ligand-centered ground-state magnetic orbital. The theoretical (14)N ligand hyperfine and quadrupole couplings also reproduce the nuclear frequencies measured by electron spin-echo envelope modulation spectroscopy. The nuclear quadrupole interaction of (187)Re is predicted to be 2 orders of magnitude larger than that of (99)Tc, in agreement with empirical simulation of the continuous-wave electron paramagnetic resonance spectrum. The spectrum of Tc(abt)(3) at high solute concentrations contains a central resonance not predicted for the isolated complex by theoretical calculations. The absence of this resonance at low solute concentrations provides evidence of intermolecular interactions in these systems.
Synthesis, structural characterization, and multifrequency electron paramagnetic resonance studies of mononuclear thiomolybdenyl complexes
Publisher: American Chemical Society (ACS)
Date: 08-03-2007
DOI: 10.1021/IC060585J
Abstract: Reaction of Tp*MoVSCl2 with a variety of phenols and thiols in the presence of triethylamine produces mononuclear, thiomolybdenyl complexes Tp*MoVSX2 [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate X = 2-(ethylthio)phenolate (etp), 2-(n-propyl)phenolate (pp), phenolate X2 = benzene-1,2-dithiolate (bdt), 4-methylbenzene-1,2-dithiolate (tdt), benzene-1,2-diolate (cat)]. The complexes have been characterized by microanalysis, mass spectrometry, IR, EPR, and UV-visible spectroscopic data, and X-ray crystallography (for the etp, pp, bdt, and cat derivatives). The mononuclear, six-coordinate, distorted-octahedral Mo centers are coordinated by terminal sulfido (MoS = 2.123(1)-2.1368(8) A), tridentate facial Tp*, and monodentate or bidentate O/S-donor ligands. Multifrequency (S-, X-, Q-band) EPR spectra of the complexes and selected molybdenyl analogues were acquired at 130 K and 295 K and yielded a spin Hamiltonian of Cs symmetry or lower, with gzz < gyy < gxx Ax'x' approximately Ay'y', and a noncoincidence angle in the range of beta = 24-39 degrees . Multifrequency EPR, especially at S-band, was found to be particularly valuable in the unambiguous assignment of the spin Hamiltonian parameters in these low-symmetry complexes. The weaker pi-donor terminal sulfido ligand yields a smaller SOMO-LUMO gap and reduced g-values for the thiomolybdenyl complexes compared with molybdenyl analogues, supporting existing crystallographic and EPR data for an apically coordinated oxo group in the active site of xanthine oxidase.
Is it time to consider prophylactic appendectomy in patients with serrated polyposis syndrome undergoing surveillance?
Publisher: BMJ
Date: 21-07-2020
Tuning the Redox Properties of Copper(II) Complexes with Amyloid-β Peptides
Publisher: The Electrochemical Society
Date: 2016
DOI: 10.1149/2.0641613JES
Development of a neuroprotective antioxidant by a mix-and-match strategy
Publisher: ScopeMed
Date: 2013
Interplay between Copper, Neprilysin, and N-Truncation of β-Amyloid
Publisher: American Chemical Society (ACS)
Date: 18-05-2018
DOI: 10.1021/ACS.INORGCHEM.8B00391
Abstract: Sporadic Alzheimer's disease (AD) is associated with an inefficient clearance of the β-amyloid (Aβ) peptide from the central nervous system. The protein levels and activity of the Zn
Spin states of C603- and C120On- (n = 2, 3, 4) anions using electron spin transient nutation spectroscopy
Publisher: American Chemical Society (ACS)
Date: 23-09-2003
DOI: 10.1021/JP035632X
The Palladium(II) Complex of Aβ4−16 as Suitable Model for Structural Studies of Biorelevant Copper(II) Complexes of N-Truncated Beta-Amyloids
Publisher: MDPI AG
Date: 02-12-2020
DOI: 10.3390/IJMS21239200
Abstract: The Aβ4−42 peptide is a major beta-amyloid species in the human brain, forming toxic aggregates related to Alzheimer’s Disease. It also strongly chelates Cu(II) at the N-terminal Phe-Arg-His ATCUN motif, as demonstrated in Aβ4−16 and Aβ4−9 model peptides. The resulting complex resists ROS generation and exchange processes and may help protect synapses from copper-related oxidative damage. Structural characterization of Cu(II)Aβ4−x complexes by NMR would help elucidate their biological function, but is precluded by Cu(II) paramagneticism. Instead we used an isostructural diamagnetic Pd(II)-Aβ4−16 complex as a model. To avoid a kinetic trapping of Pd(II) in an inappropriate transient structure, we designed an appropriate pH-dependent synthetic procedure for ATCUN Pd(II)Aβ4−16, controlled by CD, fluorescence and ESI-MS. Its assignments and structure at pH 6.5 were obtained by TOCSY, NOESY, ROESY, 1H-13C HSQC and 1H-15N HSQC NMR experiments, for natural abundance 13C and 15N isotopes, aided by corresponding experiments for Pd(II)-Phe-Arg-His. The square-planar Pd(II)-ATCUN coordination was confirmed, with the rest of the peptide mostly unstructured. The diffusion rates of Aβ4−16, Pd(II)-Aβ4−16 and their mixture determined using PGSE-NMR experiment suggested that the Pd(II) complex forms a supramolecular assembly with the apopeptide. These results confirm that Pd(II) substitution enables NMR studies of structural aspects of Cu(II)-Aβ complexes.
Pleomorphic copper coordination by alzheimer's disease amyloid-β peptide
Publisher: American Chemical Society (ACS)
Date: 02-01-2009
DOI: 10.1021/JA808073B
Abstract: Numerous conflicting models have been proposed regarding the nature of the Cu(2+) coordination environment of the amyloid beta (Abeta) peptide, the causative agent of Alzheimer's disease. This study used multifrequency CW-EPR spectroscopy to directly resolve the superhyperfine interactions between Cu(2+) and the ligand nuclei of Abeta, thereby avoiding ambiguities associated with introducing point mutations. Using a library of Abeta16 analogues with site-specific (15)N-labeling at Asp1, His6, His13, and His14, numerical simulations of the superhyperfine resonances delineated two independent 3N1O Cu(2+) coordination modes, {N(a)(D1), O, N(epsilon)(H6), N(epsilon)(H13)} (component Ia) and {N(a)(D1), O, N(epsilon)(H6), N(epsilon)(H14)} (component Ib), between pH 6-7. A third coordination mode (component II) was identified at pH 8.0, and simulation of the superhyperfine resonances indicated a 3N1O coordination sphere involving nitrogen ligation by His6, His13, and His14. No differences were observed upon (17)O-labeling of the phenolic oxygen of Tyr10, confirming it is not a key oxygen ligand in the physiological pH range. Hyperfine sublevel correlation (HYSCORE) spectroscopy, in conjunction with site-specific (15)N-labeling, provided additional support for the common role of His6 in components Ia and Ib, and for the assignment of a {O, N(epsilon)(H6), N(epsilon)(H13), N(epsilon)(H14)} coordination sphere to component II. HYSCORE studies of a peptide analogue with selective (13)C-labeling of Asp1 revealed (13)C cross-peaks characteristic of equatorial coordination by the carboxylate oxygen of Asp1 in component Ia/b coordination. The direct resolution of Cu(2+) ligand interactions, together with the key finding that component I is composed of two distinct coordination modes, provides valuable insight into a range of conflicting ligand assignments and highlights the complexity of Cu(2+)/Abeta interactions.
Outcomes of Deep Mural Injury After Endoscopic Resection: An International Cohort of 3717 Large Non-Pedunculated Colorectal Polyps
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.CGH.2021.01.007
Abstract: Although perforation is the most feared adverse event associated with endoscopic mucosal resection (EMR), limited data exists concerning its management. Therefore, we sought to evaluate the short- and long-term outcomes of intra-procedural deep mural injury (DMI) in an international multi-center observational cohort of large (≥20 mm) non-pedunculated colorectal polyps (LNPCPs). Consecutive patients who underwent EMR for a LNPCP ≥20 mm were evaluated. Significant DMI (S-DMI) was defined as Sydney DMI Classification type III (muscularis propria injury, target sign) or type IV/V (perforation without or with contamination, respectively). The primary outcome was successful S-DMI defect closure. Secondary outcomes included technical success (removal of all visible polypoid tissue during index EMR), surgical referral and recurrence at first surveillance colonscopy (SC1). Between July 2008 to May 2020, 3717 LNPCPs underwent EMR. Median lesion size was 35mm (interquartile range (IQR) 25 to 45mm). Significant DMI was identified in 101 cases (2.7%), with successful defect closure in 98 (97.0%) using a median of 4 through-the-scope clips (TTSCs IQR 3 to 6 TTSCs). Three (3.0%) patients underwent S-DMI-related urgent surgery. Technical success was achieved in 94 (93.1%) patients, with 46 (45.5%) admitted to hospital (median duration 1 day IQR 1 to 2 days). Comparing LNPCPs with and without S-DMI, no differences in technical success (94 (93.1%) vs 3316 (91.7%) P = .62) or SC1 recurrence (12 (20.0%) vs 363 (13.6%) P = .15) were identified. Significant DMI is readily managed endoscopically and does not appear to affect technical success or recurrence.
Removal of a cysteine ligand from rubredoxin: Assembly of Fe2 S2 and Fe“S-Cys”3 “OH” centres
Publisher: Springer Science and Business Media LLC
Date: 09-2002
DOI: 10.1007/S00775-002-0355-1
Abstract: The electron transfer protein rubredoxin from Clostridium pasteurianum contains an Fe(S-Cys)(4) active site. Mutant proteins C9G, C9A, C42G and C42A, in which cysteine ligands are replaced by non-ligating Gly or Ala residues, have been expressed in Escherichia coli. The C42A protein expresses with a Fe(III)(2)S(2) cluster in place. In contrast, the other proteins are isolated in colourless forms, although a Fe(III)(2)S(2) cluster may be assembled in the C42G protein via incubation with Fe(III)and sulfide. The four mutant proteins were isolated as stable mononuclear Hg(II)forms which were converted to unstable mononuclear Fe(III)preparations that contain both holo and apo protein. The Fe(III)systems were characterized by metal analysis and mass spectrometry and by electronic, electron paramagnetic resonance, X-ray absorption and resonance Raman spectroscopies. The dominant Fe(III) form in the C9A preparation is a Fe(S-Cys)(3)(OH) centre, similar to that observed previously in the C6S mutant protein. Related centres are present in the proteins NifU and IscU responsible for assembly and repair of iron-sulfur clusters in both prokaryotic and eukaryotic cells. In addition to Fe(S-Cys)(3)(OH) centres, the C9G, C42G and C42A preparations contain a second four-coordinate Fe(III)form in which a ligand appears to be supplied by the protein chain.
Resistance of Cu(Aβ4 – 16) to Copper Capture by Metallothionein‐3 Supports a Function for the Aβ4 – 42 Peptide as a Synaptic Cu
Publisher: Wiley
Date: 30-05-2016
Abstract: Aβ4-42 is a major species of Aβ peptide in the brains of both healthy in iduals and those affected by Alzheimer's disease. It has recently been demonstrated to bind Cu(II) with an affinity approximately 3000 times higher than the commonly studied Aβ1-42 and Aβ1-40 peptides, which are implicated in the pathogenesis of Alzheimer's disease. Metallothionein-3, a protein considered to orchestrate copper and zinc metabolism in the brain and provide antioxidant protection, was shown to extract Cu(II) from Aβ1-40 when acting in its native Zn7 MT-3 form. This reaction is assumed to underlie the neuroprotective effect of Zn7 MT-3 against Aβ toxicity. In this work, we used the truncated model peptides Aβ1-16 and Aβ4-16 to demonstrate that the high-affinity Cu(II) complex of Aβ4-16 is resistant to Zn7 MT-3 reactivity. This indicates that the analogous complex of the full-length peptide Cu(Aβ4-42) will not yield copper to MT-3 in the brain, thus supporting the concept of a physiological role for Aβ4-42 as a Cu(II) scavenger in the synaptic cleft.
Stable radical content and anti-radical activity of roasted arabica coffee: From in-tact bean to coffee brew
Publisher: Public Library of Science (PLoS)
Date: 09-04-2015
A density functional study of the electronic structure and spin hamiltonian parameters of mononuclear thiomolybdenyl complexes
Publisher: American Chemical Society (ACS)
Date: 17-02-2007
DOI: 10.1021/IC060586B
Abstract: The electron paramagnetic resonance spin Hamiltonian parameters of mononuclear thiomolybdenyl complexes based upon the tris(pyrazolyl)borate ligand, together with their molybdenyl analogues, are calculated using density functional theory. The electronic g matrix and 95Mo hyperfine matrix are calculated as second-order response properties from the coupled-perturbed Kohn-Sham equations. The scalar relativistic zero-order regular approximation (ZORA) is used with an all-electron basis and an accurate mean-field spin-orbit operator which includes all one- and two-electron terms. The principal values and relative orientations of the g and A interaction matrices obtained from the experimental spectra in a previous EPR study are compared with those obtained from unrestricted Kohn-Sham calculations at the BP86 and B3LYP level, and the latter are found to be in good quantitative agreement. A quasi-restricted approach is used to analyze the influence of the various molecular orbitals on g and A. In all complexes the ground state magnetic orbital is dX2-Y2-based and the orientation of the A matrix is directly related to the orientation of this orbital. The largest single contribution to the orientation of the g matrix arises from the spin-orbit coupling of the dYZ-based lowest-unoccupied molecular orbital into the ground state. A number of smaller, cumulative charge-transfer contributions augment the d-d contributions. A comparison of the theoretical EPR parameters obtained using both crystallographic and gas-phase geometry-optimized structures of Tp*MoO(bdt) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate, bdt = 1,2-benzenedithiolate) suggests a correspondence between the metal-dithiolate fold angle and the angle of noncoincidence between g and A.
Copper coordination by familial mutants of parkinson's disease-associated α-synuclein
Publisher: Springer Science and Business Media LLC
Date: 20-10-2009
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