			Home About us Contact

Copper Binding (copper + binding)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

Copper binding to octarepeat peptides of the prion protein monitored by mass spectrometry

PROTEIN SCIENCE, Issue 2 2000
Randy M. Whittal
Abstract Electrospray ionization mass spectrometry (ESI-MS) was used to measure the binding of Cu2+ ions to synthetic peptides corresponding to sections of the sequence of the mature prion protein (PrP). ESI-MS demonstrates that Cu2+ is unique among divalent metal ions in binding to PrP and defines the location of the major Cu2+ binding site as the octarepeat region in the N-terminal domain, containing multiple copies of the repeat ProHisGlyGlyGlyTrpGlyGln. The stoichiometries of the complexes measured directly by ESI-MS are pH dependent: a peptide containing four octarepeats chelates two Cu2+ ions at pH 6 but four at pH 7.4. At the higher pH, the binding of multiple Cu2+ ions occurs with a high degree of cooperativity for peptides C-terminally extended to incorporate a fifth histidine. Dissociation constants for each Cu2+ ion binding to the octarepeat peptides, reported here for the first time, are mostly in the low micromolar range; for the addition of the third and fourth Cu2+ ions to the extended peptides at pH 7.4, KD's are <100 nm. n-terminal acetylation of the peptides caused some reduction in the stoichiometry of binding at both ph's. cu2+ also binds to a peptide corresponding to the extreme N-terminus of PrP that precedes the octarepeats, arguing that this region of the sequence may also make a contribution to the Cu2+ complexation. Although the structure of the four-octarepeat peptide is not affected by pH changes in the absence of Cu2+, as judged by circular dichroism, Cu2+ binding induces a modest change at pH 6 and a major structural perturbation at pH 7.4. It is possible that PrP functions as a Cu2+ transporter by binding Cu2+ ions from the extracellular medium under physiologic conditions and then releasing some or all of this metal upon exposure to acidic pH in endosomes or secondary lysosomes. [source]

Characterization of copper binding to the peptide amyloid-,(1,16) associated with Alzheimer's disease

BIOPOLYMERS, Issue 1 2006
Qing-Feng Ma
Abstract Amyloid-, peptide (A,) is the principal constituent of plaques associated with Alzheimer's disease (AD) and is thought to be responsible for the neurotoxicity associated with the disease. Copper binding to A, has been hypothesized to play an important role in the neruotoxicity of A, and free radical damage, and Cu2+ chelators represent a possible therapy for AD. However, many properties of copper binding to A, have not been elucidated clearly, and the location of copper binding sites on A, is also in controversy. Here we have used a range of spectroscopic techniques to characterize the coordination of Cu2+ to A,(1,16) in solution. Electrospray ionization mass spectrometry shows that copper binds to A,(1,16) at pH 6.0 and 7.0. The mode of copper binding is highly pH dependent. Circular dichroism results indicate that copper chelation causes a structural transition of A,(1,16). UV-visible absorption spectra suggest that three nitrogen donor ligands and one oxygen donor ligand (3N1O) in A,(1,16) may form a type II square-planar coordination geometry with Cu2+. By means of fluorescence spectroscopy, competition studies with glycine and L -histidine show that copper binds to A,(1,16) with an affinity of Ka , 107M,1 at pH 7.8. Besides His6, His13, and His14, Tyr10 is also involved in the coordination of A,(1,16) with Cu2+, which is supported by 1H NMR and UV-visible absorption spectra. Evidence for the link between Cu2+ and AD is growing, and this work has made a significant contribution to understanding the mode of copper binding to A,(1,16) in solution. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 20,31, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

A study of the mechanisms of divalent copper binding to a modified cellulose adsorbent

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
David William O'Connell
Abstract A modified cellulose material was prepared by grafting glycidyl methacrylate to cellulose (Cell- g -GMA) with subsequent functionalization with imidazole (Cell- g -GMA-imidazole). This latter compound was used in the adsorption of copper from aqueous solution. The mechanism of Cu(II) binding onto the cell- g -GMA-imidazole was investigated at the molecular level using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) and X-ray diffraction (XRD). FTIR and Raman spectroscopy provided an insight into the extent to which perturbation of the imidazole ring occurred following adsorption of the metal while XPS spectra indicated the binding of Cu(II) ions to nitrogen atoms by the appearance of additional binding energy peaks for nitrogen on the cellulose- g -GMA-imidazole sample post adsorption. The EDX technique provided clear evidence of the physical presence of both the copper and sulfate on the cellulose- g -GMA-imidazole material post adsorption. XRD analysis further confirmed the presence of a copper species in the adsorbent material as copper sulfate hydroxide (Cu3(OH)4SO4 - antlerite). The XRD studies further suggest that the overall extent of Cu(II) adsorption is not alone a combination of true metal chelation as suggested by FTIR, Raman and XPS, but also a function of surface precipitation of the polynuclear copper species. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]