Conformational studies on polynucleotide chains. III. Intramolecular energy maps and comparison with experiments

Conformational energy maps for the four combinations of two consecutive torsional angles of the backbone structure of polydeoxyribonucleotides are presented. Both the C(2′)‐endo and the C(3′)‐endo conformation of sugar rings were considered. The energies were evaluated with an analytical expression representing the best fit to ab initio energies computed in the Hartree‐Fock approximation, and consisting of a contribution from nonbonded interactions of the Lennard‐Jones 6‐12 type and an intrinsic torsional potential. It is shown that the minima of these maps are in excellent agreement with the most stable conformations as obtained from x‐ray crystallographic analysis of nucleic acids and polynucleotides.