NONPLANAR GEOMETRIES OF DNA BASES - AB-INITIO 2ND-ORDER MOLLER-PLESSET STUDY

Authors
Citation
J. Sponer et P. Hobza, NONPLANAR GEOMETRIES OF DNA BASES - AB-INITIO 2ND-ORDER MOLLER-PLESSET STUDY, Journal of physical chemistry, 98(12), 1994, pp. 3161-3164
Citations number
23
Categorie Soggetti
Chemistry Physical
ISSN journal
00223654
Volume
98
Issue
12
Year of publication
1994
Pages
3161 - 3164
Database
ISI
SICI code
0022-3654(1994)98:12<3161:NGODB->2.0.ZU;2-I
Abstract
Interactions of DNA bases represent a crucial source of DNA conformati onal variability. Oligonucleotide crystal studies revealed a number of base-base interactions which seem to be stabilized by nonplanar DNA b ase amino groups. Therefore, an accurate description of the geometry a nd deformability of the DNA base amino groups is very important. Here, the second-order Moller-Plesset (MP2) 6-31G-optimized nonplanar geom etries of adenine, cytosine, guanine, thymine, and isocytosine are pre sented. The amino groups of the bases exhibit significant Sp3 pyramida lization. The dihedral angles between the cytosine and adenine rings a nd their amino group hydrogen atoms range from 10 to 25-degrees, and t he nonplanar cytosine and adenine are 0.4 kcal/mol more stable than th e planar molecules. Dihedral angles between the two guanine amino grou p hydrogen atoms and the guanine ring are 43 and 12-degrees, and the n onplanar guanine is 1.6 kcal/mol more stable than the planar molecule. Isocytosine exhibits amino group properties similar to those of guani ne. Selected DNA bases were also optimized using larger basis sets of atomic orbitals: 6-31G*, DZP+, and DZ(2d). The MP2/6-31G** calculatio ns yield results very similar to those of the MP2/6-31G calculations, while the larger DZP+ and DZ(2d) basis sets indicate an even greater amino group nonplanarity.