The testing of technique for modeling the local atomic structure and X-ray absorption spectra for zinc ions in an aqueous solution in the presence of arachidic acid has been adjusted. Models of the local structure of zinc with different coordination geometries are considered: planar, pyramidal, tetrahedral, and octahedral. The cases of increasing distances between the zinc ion and water molecules in the plane and in the axial direction are simulated for octahedral coordination. It has been established that the most probable change in the local structure of the zinc environment in solution in the presence of arachidic acid is the removal of water molecules from zinc ions in the axial position and their further replacement with the formation of a bond with the carboxyl group of arachidic acid.

Keywords: arachidic acid, lipid layer, local atomic structure, X-ray absorption spectroscopy, total external reflection, zinc, biomembrane, finite difference method, monolayer

The study of copper ion (Cu2+) environment in aqueous solution was performed by means of X-ray absorption spectroscopy. X-ray absorption spectra for various concentrations of aqueous solutions of CuCl2 were measured. The testing of near-edge fine structure approach for calculating X-ray absorption Cu K-edge spectra of copper ion (Cu2 +) coordinated complex by finite difference method for solution of Schrödinger equation were held . A model of local environment of copper ion (Cu2 +) in aqueous solutions is proposed.

Keywords: X-ray absorption spectroscopy, 3d-metals ions, aqueous solutions, local environment, finite difference method, coordination complexes

A study of X-ray absorption spectra depending solution of copper (II) and cobalt from the time of preparation of these solutions (immediately prior to the measurement and aged for six months), as well as the dependence of the spectra on the acidity of the solution (different levels of pH 5.7 and 1, which is achieved by addition of hydrochloric acid). Processing of the experimental spectra were in the software package Athena. The study established according to the experimental X-ray absorption spectra of the solution of copper (II) and cobalt chloride on the test conditions.

Keywords: X-ray absorption spectroscopy, soft X-rays, copper chloride, copper (II), cobalt chloride aqueous solution, X-ray absorption spectrometer Rigaku R-XAS, a cell with kapton window

Alzheimer's disease is an incurable illness. It affects about half a million people in Russia, and due to the general trend towards aging of the population the number of Alzheimer's disease cases will steadily increase. Insoluble deposits of amyloid beta in the brain tissue (amyloid plaques) are the major morphological characteristic of Alzheimer's disease. It has been found that the increased concentration of copper in amyloid plaques results in copper ions bound to the protein. It is the presence of copper in the binding site triggers of the formation of amyloid plaques. Therefore, the study of the binding site in amyloid beta is of great scientific interest. The local atomic structure of the Cu(I) copper ion binding site in the amyloid beta peptide has been studied by means of XANES spectroscopy. Several model structures obtained by molecular mechanics and density functional theory (ADF code) have been tested. Theoretical analysis of X-ray absorption spectra based on the finite difference method implemented in FDMNES code was performed. An appropriate model structure of the Cu(I) copper ion binding site in amyloid beta peptide has been found.

Keywords: amyloid beta, binding site, Alzheimer's disease, the method of finite differences, Cu(I)