Search results for "Copper"
showing 10 items of 3029 documents
Thermal aggregation and ion-induced cold-gelation of bovine serum albumin
2009
Protein cold-gelation has recently received particular attention for its relevance in bio and food technology. In this work, we report a study on bovine serum albumin cold-gelation induced by copper or zinc ions. Metal-induced cold-gelation of proteins requires two steps: during the first one, the heat treatment causes protein partial unfolding and aggregation; then, after cooling the solution to room temperature, gels are formed upon the addition of metal ions. The thermally induced behaviour has been mainly investigated through different techniques: Fourier transform infrared (FTIR) spectroscopy, circular dichroism, dynamic light scattering (DLS) and rheology. Data have shown that the agg…
Formation of a novel ferromagnetic end-to-end cyanate bridged homochiral helical copper(ii) Schiff base complex via spontaneous symmetry breaking
2014
A homochiral helical coordination polymer of copper(II) has been synthesized using achiral precursors via spontaneous symmetry breaking and has been confirmed by single crystal X-ray diffraction and solid-state CD spectroscopy. The variable temperature magnetic measurements indicate the presence of weak ferromagnetic exchange interactions mediated by end-to-end cyanate bridges (J = +0.12 cm(-1)).
Aß(25-35) and its C-and/or N-blocked derivatives: copper driven structural features and neurotoxicity
2006
The toxic properties of beta-amyloid protein, Abeta(1-42), the major component of senile plaques in Alzheimer's disease, depend on nucleation-dependent oligomerization and aggregation. In addition, Abeta(1-42) toxicity is favored by the presence of trace metals, which affect the secondary structure of the peptide. A peptide comprising 11 residues within Abeta(1-42) [Abeta(25-35)] aggregates and retains the neurotoxic activity of Abeta(1-42). We have used both Abeta(25-35) and its C-amidated or N-acetylated/C-amidated derivatives to investigate the role of copper(II) in modulating the conformation and aggregation state as well as the neurotoxic properties of amyloid peptides. Electrospray io…
Metal NHC Complexes with Naphthalimide Ligands as DNA-Interacting Antiproliferative Agents
2017
Naphthalimide-based N-heterocyclic carbene (NHC) complexes of the type [(1,5-cyclooctadiene)(NHC)RhCl)] (4 a-c), [(p-cymene)(NHC)RuCl2 )] (5 a-c), and [(NHC)CuBr] (6 a-c) were synthesized and investigated as antiproliferative agents that target DNA. The cytotoxic effects were largely driven by the naphthalimide structure, which is a DNA-intercalating moiety. Regarding the metal center, the highest activities were observed with the rhodium complexes, and cytotoxic activity was significantly lower for the ruthenium derivatives. The stable coordination of the NHC ligands of selected complexes 4 b and 5 b in solution was confirmed, and their DNA binding properties were studied by UV/Vis spectro…
Enantiomerically pure trinuclear helicates via diastereoselective self-assembly and characterization of their redox chemistry.
2014
A tris(bipyridine) ligand 1 with two BINOL (BINOL = 2, 2′-dihydroxy-1, 1′-binaphthyl) groups has been prepared in two enantiomerically pure forms. This ligand undergoes completely diastereoselective self-assembly into D2-symmeteric double-stranded trinuclear helicates upon coordination to copper(I) and silver(I) ions and to D3-symmetric triple-stranded trinuclear helicates upon coordination to copper(II), zinc(II), and iron(II) ions as demonstrated by mass spectrometry, NMR and CD spectroscopy in combination with quantum chemical calculations and X-ray diffraction analysis. According to the calculations, the single diastereomers that are formed during the self-assembly process are strongly …
Nickel(II), copper(II) and zinc(II) metallo-intercalators: structural details of the DNA-binding by a combined experimental and computational investi…
2014
We present a thorough characterization of the interaction of novel nickel(II) (1), copper(II) (2) and zinc(II) (3) Schiff base complexes with native calf thymus DNA (ct-DNA), in buffered aqueous solution at pH 7.5. UV-vis absorption, circular dichroism (CD) and viscometry titrations provided clear evidence of the intercalative mechanism of the three square-planar metal complexes, allowing us to determine the intrinsic DNA-binding constants (K(b)), equal to 1.3 × 10(7), 2.9 × 10(6), and 6.2 × 10(5) M(-1) for 1, 2 and 3, respectively. Preferential affinity, of one order of magnitude, toward AT compared to GC base pair sequences was detected by UV-vis absorption titrations of 1 with [poly(dG-d…
Luminescent P-Chirogenic Copper Clusters
2013
P-chirogenic clusters of the cubanes [Cu4I4L4] (L = chiral phosphine) were prepared from (+)- and (-)-ephedrine with L = (S)- or (R)-(R)(Ph)(i-Pr)P (with R = CH3 (seven steps) or C17H35 (10 steps)) with e.e. up to 96%. The X-ray structure of [Cu4I4((R)-(CH3)(Ph)(i-Pr)P)4] confirmed the cubane structure with average Cu···Cu and Cu···I distances of 2.954 and 2.696 Å, respectively. The cubane structure of the corresponding [Cu4I4((S)-(CH3)(Ph)(i-Pr)P)4] was established by the comparison of the X-ray powder diffraction patterns, and the opposite optical activity of the (S)- and (R)-ligand-containing clusters was confirmed by circular dichroism spectroscopy. Small-angle X-ray scattering patterns…
Fast Matrix Multiplication
2015
Until a few years ago, the fastest known matrix multiplication algorithm, due to Coppersmith and Winograd (1990), ran in time O(n2.3755). Recently, a surge of activity by Stothers, Vassilevska-Williams, and Le~Gall has led to an improved algorithm running in time O(n2.3729). These algorithms are obtained by analyzing higher and higher tensor powers of a certain identity of Coppersmith and Winograd. We show that this exact approach cannot result in an algorithm with running time O(n2.3725), and identify a wide class of variants of this approach which cannot result in an algorithm with running time $O(n^{2.3078}); in particular, this approach cannot prove the conjecture that for every e > 0, …
Molecular Dynamics Study of Copper and Aluminum under Mechanical Strain
1998
AbstractMechanical properties of copper and aluminum have been studied using finite temperature molecular dynamics simulations. Atomic interactions have been described by a many-atom effective medium potential, which takes into account interactions up to third neighbors. The computed elastic constants showed good agreement with experimental data. Encouraged by these results the model was applied to study fracture in copper. Systems with a grain boundary and an initial cut serving as a crack seed have been studied. In the first case, crack nucleation and propagation took place exclusively at the grain boundary. In the second case, dislocation propagation was observed in one of the <110>…
Localized Surface Plasmon Resonance in Colloidal Copper Sulphide (Cu2-xS, x = 0 ≤ x < 1) Nanocrystals and Its Applications
2021
Colloidally prepared copper sulphide (Cu2-xS) nanocrystals are possessing superior structural and optical properties owing to the presence of copper vacancies. The application of colloidal Cu2-xS nanocrystals are critically analysed for several optoelectronic applications. Furthermore, colloidally prepared Cu2-xS nanocrystals undergo facile process such as cation exchange, additives induced structural modifications etc. Therefore, it is important to evaluate the optical properties of these nanomaterials in order to apply them for future optoelectronic applications. Out of other properties, localized surface plasmon resonance (LSPR) by controlling composition of the Cu2-xS nanocrystals is in…