Interactions between nucleic acid bases

The pairing and stacking energies of nucleic acid bases have been computed by the perturbation formulas from reliable eigenvalues and wavefunctions involving all valence electrons for the bases and for the base pairs. The position of minimal energies for the electrostatic components, `corresponding to a free rotation of one base pair around the helix axis to a fixed vertical distance between two monomers equal to 3·36 Å, will reach angles around 45 °, whilst the minima of dispersion and exchange components will not reach angles higher than 18 °. Consequently, the angle for the minima of total energy, although not directly computable, is reasonably expected to be around 36 °. © 1972.