2010
Volume 10, Number 2, p.p. 71–73
Quantum-chemical description of the influence of electronic effects of proton transfer in guanine–cytosine base pairs
T. Zarqua,1 J. Kereselidze1, * and Z. Pachulia2
1 Department of Chemistry, I.Javakhishvili Tbilisi State University, 0128 Tbilisi, Georgia
2 Department of Chemistry, Sokhumi State University, 0114 Tbilisi, Georgia
The electronic and energetic characteristics of process of the proton transfer in the 5- and 6-substituents of the guanine–cytosine base pair were calculated by means of the quantum-chemical DFT (density functional theory) method. On the basis of the analysis, the conclusion is that the electron-donor methyl group in 6th position causes an increase of charge on the N3 and N7 atoms (qN3 and qN7) of the pyrimidine ring of cytosine together with an increasing frequency of single-point mutations (Nm). However, in the case of 5-CH3, the frequency of mutation increase is more considerable for a small increase of qN3. This is apparently explained by a reduction of the bond orders participating in proton transfer. The decrease of bond orders is the reason for the increase of frequency of mutation for the 5- and 6-Cl substituent of the guanine–cytosine base pair. The charge on the heterocyclic imine atom N3 is a reliable index of reactivity of the process of proton transfer in guanine–cytosine base pairs.