It should be noted that the energy improvement obtained
due to nonplanarity of the base pairs (at least
for the G–C base pair) is very small in the present calculation.
In the real DNA double strands, the effect of
temperature may be rather large in comparison with a
few tenth kcal/mol, so that base pairs may vibrate
around the nonplanar structure. Nevertheless assuming
that the planar structure of the base pairs represents
an energy minimum then switching to the nonplanar
structure would require additional energy expense, while
our computations show that the at least G–C base pair
already possess the necessary propeller-twisted geometry
being an energy minimum.