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ABSTRACT:The aim of this study is to investigate changes in functional properties of active sites of deoxyhemoglobin upon substitution of Fe by the other 3d-metal atoms. Relationships between parameters of electronic structure, chemical binding, and temperatures of structure stability loss of active sites of ␣-and ␤-subunits of deoxyhemoglobin are estimated using the X ␣ -DV method. It is shown that the calculation technique of the temperature T m of structure stability loss of active sites of deoxyhemoglobin based on the thermodynamic uncertainty relation gives a reasonable interpretation of the maximal possible temperature for a human body living. Temperatures of structure stability loss are higher for Cr, Mn atoms (89, 42°C) and lower for Co, Ni, Cu, Zn (40, 37, 33, 29°C) in comparison with Fe (41°C). Thus the calculations performed show that the temperature of structure stability loss is controlled both by the type of the 3d atom carrying oxygen and small structural differences in active sites of ␣-and ␤-subunits of deoxyhemoglobin.

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ABSTRACT:In this work, the presence of 3d metal (MATi, V, Cr and Ni) impurity atoms in the cubic silicon carbide (3C-SiC) was simulated theoretically. Electronic structure, parameters of chemical bonding, and binding energies were calculated by the cluster density functional theory DFT approach for M substitutions in silicon, carbon, and interstitial sites. The full-potential FLMTO technique was employed to calculate the cohesive energy for the M 3 Si substitutions and the crystal lattice relaxation effects around the impurity atoms. We found that for stoichiometric substitutions all 3d impurities occupy Si positions but for nonstoichiometric SiC the Ti, V(Ni), and Cr atoms may also occupy the interstitial, Si, and C sites, respectively.

Ab initio X! discrete variation method was used for calculation of quadrupole splitting for the rough heme models in !-and β-subunits of tetrameric deoxyhemoglobin accounting small stereochemical variations. The differences of theoretical values of quadrupole splitting for these heme models were obtained.

ABSTRACT:The nonempirical X ␣ -discrete-variation cluster method was used for a quantum chemistry investigation of interactions between a hydrogen atom and other atoms in systems of practical interest: M-H (MATi, V, Cr, Fe, Ni) and TaV 2 :H. We have calculated the parameters of chemical binding between M and H atoms: degree of ionicity (␣), covalency (␤), metallicity (␥), coefficient of bond elasticity (k), and reduced binding energy E bin . On the basis of the results obtained for M-H (MATi, V, Cr, Fe, Ni), we have formulated the main trends of chemical binding and used these conclusions for the system TaV 2 :H.

ABSTRACT:The structure of the short-range surrounding of aluminum, ferric iron and Me are displaced considerably relative to the initial ideal structure. The displacement depends on the central cation of the cluster. The estimated short-range order parameters including the oxygen parameter u of the spinel are in satisfactory agreement with experimental data. Comparable analysis of the electronic structure of Al, Fe, Cr cations in octahedral positions of the spinel in ideal and relaxed clusters showed that octahedral distortions should be taken into account when interpreting spectroscopic parameters of the natural spinels and evaluating the charge balance in their structure.