Book of Abstracts: Albany 2003
June 17-21 2003
The Geometry of Canonical Watson-Crick DNA Base Pairs: Ab Initio Post-Hartree-Fock Theory Studies
Full geometry optimization (without any constrains on the planarity of the systems) was carried out for the canonical Watson-Crick base pairs at the second-order Møller-Plesset perturbation level (MP2) of theory with the 6-31G*(0.25) and 6-31G* basis sets. The correlated calculations are done within the frozen core approximation.
In Table I collected the calculated bond lengths of the bases in the A-T and G-C base pairs optimized at the MP2 correlated level with the 6-31G* basis set. The corresponding data obtained at the HF/6-31G** level are given in parentheses.
The comparison of these data shows noticeable influence of electron correlation effects on the bond lengths. For overwhelming majority of bonds in the base pairs the predicted MP2 bond lengths are increased from 0.01 to 0.05 Å as compared with the analogous HF data. The largest lengthening is observed for the N7-C8 bond of adenine and guanine (about 0.05 Å).
It is shown that according to the MP2 calculations the amino group of adenine in the A-T base pair is perfect planar for 6-31G*(0.25) basis set and is planar for 6-31G* basis set. The amino group of cytosine in the G-C base pair is practically planar while amino group of guanine for both basis sets is intrinsically non-planar.
V. I. Danilov1
1Institute of Molecular Biology and Genetics