Quantum chemical studies on the conformational structure of nucleic acids III. Calculation of backbone structure by extended Huckel theory

Abstract

Extended Huckel theory has been used to calculate the torsional angles (φ', ω', ω, φ, Ψ) for the sugar phosphate bonds which lead to stable conformations. The predicted conformations are in good agreement with the experimental observations on nucleosides, nucleotides and polynucleotides. It appears that in a double helical structure, the nonbonded and "stacking" interactions provide the stability to the conformational structure of each strand and these strands are then struck together by hydrogen bonds. The unwinding of the double helix, most likely, occurs through internal rotations about O3'-P and/or P-O5' bonds.