New data gives new interpretations...

  1. Z-d(CGCG)2 is stabilized (inter alia) by a short contact between a carbon on the guanine and the ribose ether oxygen, of which there are four per four base pairs.
  2. These contacts are replaced in B-d(CGCG)2 by NH hydrogen bonded contacts to the ribose ether oxygen.
  3. In Z-d(ATAT)2, the O-contacts to the adenine are much longer, which
  4. in B-d(ATAT)2, are replaced by short CH...O contacts.