Sl. Price et al., WHAT BASE PAIRINGS CAN OCCUR IN DNA - A DISTRIBUTED MULTIPOLE STUDY OF THE ELECTROSTATIC INTERACTIONS BETWEEN NORMAL AND ALKYLATED NUCLEIC-ACID BASES, Journal of the Chemical Society. Faraday transactions, 89(18), 1993, pp. 3407-3417
Citations number
52
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
Ab initio distributed multipole electrostatic calculations are used to
predict likely nucleic acid base pair structures for both the gas pha
se and within a double helical backbone, as represented by simple cons
traints. The resulting structures are interpreted by comparison with a
n analysis of the experimental variation of base pair geometries found
in oligonucleotide crystals. Our calculations on all pairs of the nor
mal bases (G, A, T, C) correctly predict all the multiply hydrogen-bon
ded structures, in agreement with supermolecule SCF calculations, and
also predict some new low-energy structures. Consideration of the heli
cal constraints confirms that the Watson-Crick G . C and A . T pairing
s are most favourable for inclusion in DNA, but certain mismatch base
pairs, G . T and G . A, are also energetically favourable and their ge
ometries correspond to the experimentally observed wobble conformation
s. This approach is also used to study the effect of the O6 methylatio
n of guanine which can form a doubly hydrogen-bonded Watson-Crick-like
structure with thymine. However, there are also a range of O6-methylg
uanine . cytosine structures which fit into the helical backbone and a
re energetically competitive. Thus the mutation-inducing effects of th
is base modification are likely to be very sensitive to the exact sequ
ence and local conformation of the DNA.