Nonplanar structure of the isolated N-methylated
Watson–Crick A–T base pair was also predicted by
the semiempirical SCC-DFTB-D method , where
the propeller twist angle is equal to 4 whereas sum of
amino group valence angles is equal to 360. Recently
168 N. Kurita et al. / Chemical Physics Letters 404 (2005) 164–170