Abstract
For the first time, on the quantum-mechanical level of theory MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p), a full set of hydrogen (H)-bonded hetero associates m 9 Ade·m 1 Ura in the main tautomeric forms consisting of 18 different structures was obtained. Their structural and energetical parameters were characterized and basic physical and chemical characteristics of intermolecular H-bonds that stabilize the investigated complexes were described. It was shown that global minimum of Gibbs free energy corresponds to Hoogsteen pair, after it with a small margin follow Watson–Crick pair, inverse Hoogsteen pair and inverse Watson–Crick pair. It was found that in stabilization of identified hetero associates four types of H-bonds – NH...O, NH...N, CH...O and CH...N are involved. In this case non-canonical CH...O and CH...N bonds show a linear dependence of energy on electron density in the corresponding critical point. Obtained data may be useful for experimental interpretation of the features of non-canonical base pairs association by common methods of spectroscopy, including NMR and vibrational spectroscopy. They are also important for understanding the problem of mutational variability that is caused by formation of non-complementary pairs of nucleotide bases whose role is not clear yet. Keywords: quantum chemistry, hetero associates of nucleotide bases, hydrogen bonds, adenine, uracil.
Highlights
Nucleic acids are macromolecular components of cells that play an important role in the conservation and transmission of genetic information
The presence of two complementary pairs of nucleotide bases, namely Gua·Cyt and Ade·Thy, provides a unique ability of genetic material to replicate with high accuracy
The H-bonded hetero associates of adenine (Ade) and uracil (Ura), methylated on the 9th and 1st position of nitrogen atom respectively, which are in the main tautomeric form were studied
Summary
Nucleic acids are macromolecular components of cells that play an important role in the conservation and transmission of genetic information. It inspirates researchers to use calculations, including quantum-chemical methods, to receive this biologically important information
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