Oxindole-Schiff base copper(II) complexes interactions with human serum albumin: Spectroscopic, oxidative damage, and computational studies

CD and EPR were used to characterize interactions of oxindole-Schiff base copper(II) complexes with human serum albumin (HSA). These imine ligands form very stable complexes with copper, and can efficiently compete for this metal ion towards the specific N-terminal binding site of the protein, consisting of the amino acid sequence Asp-Ala-His. Relative stability constants for the corresponding complexes were estimated from CD data, using the protein as competitive ligand, with values of log K(CuL) in the range 15.7-18.1, very close to that of [Cu(HSA)] itself, with log K(CuHSA) 16.2. Some of the complexes are also able to interfere in the a-helix structure of the protein, while others seem not to affect it. EPR spectra corroborate those results, indicating at least two different metal species in solution, depending on the imine ligand. Oxidative damage to the protein after incubation with these copper(II) complexes, particularly in the presence of hydrogen peroxide, was monitored by carbonyl groups formation, and was observed to be more severe when conformational features of the protein were modified. Complementary EPR spin-trapping data indicated significant formation of hydroxyl and carbon centered radicals, consistent with an oxidative mechanism. Theoretical calculations at density functional theory (DFT) level were employed to evaluate Cu(II)-L binding energies, L -> Cu(II) donation, and Cu(II) -> L back-donation, by considering the Schiff bases and the N-terminal site of HSA as ligands. These results complement previous studies on cytotoxicity, nuclease and pro-apoptotic properties of this kind of copper(II) complexes, providing additional information about their possibilities of transport and disposition in blood plasma. (C) 2009 Elsevier Inc. All rights reserved.

The interaction between atoms of Au and Cu with clean Si(111) surface: A study combining synchrotron radiation grazing incidence X-ray fluorescence analysis and theoretical calculations

In order to evaluate the interactions between Au/Cu atoms and clean Si(l 11) surface, we used synchrotron radiation grazing incidence X-ray fluorescence analysis and theoretical calculations. Optimized geometries and energies on different adsorption sites indicate that the binding energies at different adsorption sites are high, suggesting a strong interaction between metal atom and silicon surface. The Au atom showed higher interaction than Cu atom. The theoretical and experimental data showed good agreement. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Dynamics and Heterogeneity of Pb(II) Binding by SiO2 Nanoparticles in an Aqueous Dispersion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Crystal structure, DNA binding studies, nucleolytic property and topoisomerase I inhibition of zinc complex with 1,10-phenanthroline and 3-methyl-picolinic acid

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The Leishmania amazonensis TRF ( TTAGGG repeat-binding factor) homologue binds and co-localizes with telomeres

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Activity and characterization by XPS, HR-TEM, Raman spectroscopy, and BET surface area of CuO/CeO2-TiO2 catalysts

Structural and textural studies of a CuO/TiO2 System modified by cerium oxide were conducted using Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N-2 absorption (BET specific surface area). The introduction of a minor amount of CeO2 (Ce0.09Ti0.82O1.91CU0.09 sample) resulted in a material with the maximum surface area value. The results of Raman spectroscopy revealed the presence of only two crystalline phases, TiO2 anatase and CeO2 cerianite, with well-dispersed copper species. TEM micrographs showed a trend toward smaller TiO2 crystallites when the cerium oxide content was increased. The XPS analysis indicated the rise of a second peak in Ti 2p spectra with the increasing amount of CeO2 located at higher binding energies than that due to the Till in a tetragonal symmetry. The CuO/TiO2 system modified by CeO2 displayed a superior performance for methanol dehydrogenation than the copper catalyst supported only on TiO2 or CeO2.

X-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and x-ray diffraction characterization of CuO-TiO2-CeO2 catalyst system

X-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and x-ray absorption spectroscopy (XAS) techniques have been applied to characterize the surface composition and structure of a series of CuO-TiO2-CeO2 catalysts. For a small loading of cerium, ceria was mainly dispersed on the titania surface and a minor amount of CeO2 crystallite appeared. At higher loading of cerium, the CeO2 phase increased and the atomic Ce/Ti ratio values were smaller than the nominal composition, as a consequence of cerium agglomeration. This result suggests that only a fraction of cerium can be spread on the titania surface. For titanium-based mixed oxide, we observed that cerium is found as Ce3+ uniquely on the surface. The atomic Cu/(Ce+Ti) ratio values showed no influence from cerium concentration on the dispersion of copper, although the copper on the surface was shown to be dependent on the cerium species. For samples with a high amount of cerium, XPS analysis indicated the raise of second titanium species due cerium with spin-orbit components at higher binding energies than those presented by Ti4+ in a tetragonal structure. The structural results obtained by XAS are consistent with those obtained by XRD and XPS. (C) 2001 American Vacuum Society.

The Influence of Solutes on the Enthalpy/Entropy Change of the Actinomycin D Binding to DNA: Hydration, Energy Compensation and Long-Range Deformation on DNA

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Collision of positronium with atoms, molecules and ions using a modified coupled-channel framework

Scattering of positronium (Ps) from atoms (H, He, Ne, Ar), molecule (H(2)) and ion (He(+)) have been investigated using a coupled-channel (CC) formalism with a regularised non-local exchange potential. The advantage of using such a regularized exchange potential in the close-coupling formalism and the normalizability aspect of the solution at low energies with a minimum effective coupling are discussed. Results for the elastic and total scattering cross-sections, resonance and binding energies in Ps-H, and pick-off annihilation results in Ps-He are found to be in excellent agreement with measurements and variational predictions. (C) 2000 Elsevier B.V. B.V. All rights reserved.

S-, P- and D-wave resonances in positronium-sodium and positronium-potassium scattering

Scattering of positronium (Ps) by sodium and potassium atoms has been investigated employing a three-Ps-state coupled-channel model with Ps(ls,2s,2p) states using a time-reversal-symmetric regularized electron-exchange model potential fitted to reproduce accurate theoretical results for PsNa and PsK binding energies. We find a narrow S-wave singlet resonance at 4.58 eV of width 0.002 eV in the Ps-Na system and at 4.77 eV of width 0.003 eV in the Ps-K system. Singlet P-wave resonances in both systems are found at 5.07 eV of width 0.3 eV. Singlet D-wave structures are found at 5.3 eV in both systems. We also report results for elastic and Ps-excitation cross sections for Ps scattering by Na and K.

Three- and Four-Nucleon Bound States in Three Dimensions, Without PW Decomposition

A brief review of a three-dimensional (3D) numerical method to solve few-nucleon bound and scattering states, without the standard partial-wave (PW) decomposition, is presented. The approach is applied to three-and four-nucleon bound states, by considering the solutions of the corresponding Faddeev-Yakubovsky (FY) integral equations in momentum space. Realistic spin-isospin dependent 3D and PW formalism are presented for the alpha particle and the triton binding energies, with numerical results given in both schemes for comparison.

Universality and Scaling Limit of Weakly-Bound Tetramers

The occurrence of a new limit cycle in few-body physics, expressing a universal scaling function relating the binding energies of two successive tetramer states, is revealed by considering a renormalized zero-range two-body interaction in bound state of four identical bosons. The tetramer energy spectrum is obtained by adding a boson to an Efimov bound state with energy B-3 in the unitary limit (for zero two-body binding energy or infinite two-body scattering length). Each excited N-th tetramer energy B-4((N)) is shown to slide along a scaling function as a short-range four-body scale is changed, emerging from the 3+1 threshold for a universal ratio B-4((N))/B-3 = 4.6, which does not depend on N. The new scale can also be revealed by a resonance in the atom-trimer recombination process.

Solutions of the bound-state Faddeev-Yakubovsky equations in three dimensions by using NN and 3N potential models

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The interaction between atoms of Au and Cu with clean Si(111) surface: A study combining synchrotron radiation grazing incidence X-ray fluorescence analysis and theoretical calculations

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis and characterization of ZnO and ZnO : Ga films and their application in dye-sensitized solar cells

Highly crystalline ZnO and Ga-modified zinc oxide (ZnO:Ga) nanoparticles containing 1, 3 and 5 atom% of Ga3+ were prepared by precipitation method at low temperature. The films were characterized by XRD, BET, XPS and SEM. No evidence of zinc gallate formation (ZnGa2O4), even in the samples containing 5 atom% of gallium, was detected by XRD. XPS data revealed that Ga is present into the ZnO matrix as Ga3+, according to the characteristic binding energies. The particle size decreased as the gallium level was increased as observed by SEM, which might be related to a faster hydrolysis reaction rate. The smaller particle size provided films with higher porosity and surface area, enabling a higher dye loading. When these films were applied to dye-sensitized solar cells (DSSCs) as photoelectrodes, the device based on ZnO: Ga 5 atom% presented an overall conversion efficiency of 6% (at 10 mW cm(-2)), a three-fold increase compared to the ZnO-based DSSCs under the same conditions. To our knowledge, this is one of the highest efficiencies reported so far for ZnO-based DSSCs. Transient absorption (TAS) study of the photoinduced dynamics of dye-sensitized ZnO:Ga films showed that the higher the gallium content, the higher the amount of dye cation formed, while no significant change on the recombination dynamics was observed. The study indicates that Ga-modification of nanocrystalline ZnO leads to an improvement of photocurrent and overall efficiency in the corresponding device.