Recently it was suggested [33] that more globally, an
incipient chirality is created apparently when a planar
base connects to a nonplanar one, giving the base pair
a right- or left-handed sense, on its own. It is believed
that DNA double-helices form when a series of subunits
bind to each other in a regular way to take advantage of
a stacking of the bases. It is possible that the direction of
the helix twist can be traced to the nonplanar character
of the purine bases. The degree of this nonplanarity
could be influenced by attached solvent molecules or
other environmental factors. Further experiments and
calculations will be necessary to answer these interesting
questions.