Biomedical subjects

Grigory Smolentsev

Publications and source records attributed to Grigory Smolentsev.

3 recordsLinked to original sources

PubMed2006

Valence-to-core X-ray emission spectroscopy identification of carbide compounds in nanocrystalline Cr coatings deposited from Cr(III) electrolytes containing organic substances.

Valence-to-core X-ray emission spectroscopy was applied to study a composition of chromium coatings electrodeposited from Cr(III) sulfate electrolytes with the addition of formic or oxalic acid. It was shown that the obtained crystallographically amorphous deposits contain chromium carbide compounds. These results indicate that nanodimensional Cr crystallites formed during the electrodeposition process are characterized by very high electrocatalytic activity.

Journal Article↗

PubMed2005

Quantitative local structure refinement from XANES: multi-dimensional interpolation approach.

A new method to determine local structure in terms of a few structural parameters is proposed and realised in FitIt software. It is based on fitting of X-ray absorption near-edge structure (XANES) spectra using the combination of full multiple-scattering calculations, and multi-dimensional interpolation of spectra as a function of structural parameters. The procedure is divided into two steps: the construction of an interpolation polynomial, and the fitting of experimental spectra using the interpolation polynomial. During the construction of the polynomial, multiple-scattering calculations for certain sets of structural parameters are needed. The strategy for the selection of the most important expansion terms and corresponding sets of structural parameters is proposed. Fitting of the spectrum using multi-dimensional interpolation is very fast (a few seconds) because multiple-scattering calculations are unnecessary during this step. Also, this approach allows the development of a visual interface with the possibility of seeing the spectrum that corresponds to any set of structural parameters immediately. Thus, using a very limited number of multiple-scattering calculations, which are most time-consuming, it is possible to fit XANES. The interpolation polynomial construction procedure for three model molecules, FeS4, FeO6 and Ni(CN)4, is demonstrated. An additional test has been performed for the latter most-complex example to check the assumption that a minimum of discrepancy between theoretical and experimental spectra corresponds only to the correct structure of the complex. A comparison with another XANES fitting software, MXAN, is given.

Algorithms↗

PubMed2004

Axial ligation of Fe(II)-bleomycin probed by XANES spectroscopy.

Full multiple scattering calculations of the Fe K-edge X-ray absorption near edge structure of bleomycin have been performed. Structural insight is based on the comparison between experimental and theoretical data calculated for different active site models coming from NMR-informed molecular dynamic simulations. In all models considered, the equatorial ligands (secondary amine in beta-aminoalanine, pyrimidine and imidazole rings and the beta-hydroxyhistidine) were left unchanged. Seven models with two axial ligands (the primary amine in beta-aminoalanine and the carbomoyl group of the mannose or a solvent molecule) were tested. The best agreement between theoretical and experimental spectra is achieved for the model of bleomycin with the primary amine and the oxygen of the mannose sugar occupying the axial positions. The coordination environment is characterized by serious distortions of the Fe octahedron, including the presence of one ligand with a very short bond length and significant angular distortions.

Bleomycin↗