Influence of complex formation on physical properties of nucleic acid components

Abstract

Calculations of bond lengths, IR spectra, and the electronic structure of major nucleic acid bases, complexes: 5-azacytosine-guanine, 5-azacytosine-guanine with 8 molecules of water, 5-azacytosine with 5 molecules of water, and complexes adenine tautomers with Zn²⁺ were carried out by MP2 and DFT methods. It was shown that modern calculation methods (MP2 and DFT) with basis set 6-31**G allow due to calculating quit well (within 1%) length of carbonyl bonds in nucleic acid components and to estimate its changes when complexes are forming. An estimation of the length of the carbonyl bond was made on the basis of experimental and calculated data, depending on the number of hydrogen bonds formed. An empirical dependence between the bond length of the carbonyl group and its vibration frequency was built. A significant charge transfer followed by the re-distribution of electron density on the adenine molecule takes place when complexes of adenine tautomers with Zn²⁺ ions are forming.