The conformation of poly(dG-dC)·poly(dG-dC), poly(dG)·poly(dC), and calf thymus DNA modified with N-acetoxy-N-2-acetylaminofluorene (N-acetoxy-AAF) was examined by extent of reaction with anti cytidine antibodies. In contrast to modified poly(dG)·poly(dC) and DNA, modified poly(dG-dC)·poly(dG-dC) failed to react with the antibodies indicating that the base pairing in this polymer is intact. This is consistent with induction of the Z-DNA conformation in AAF modified poly(dG-dC)·poly(dG-dC). Using minimized potential energy calculations on the dCpdG-AAF dimer as a model for the modified polymer, it is shown that the proposed Z-DNA conformation is energetically stable. A model is proposed for an AAF modified tetramer, dGpdCpdGpdC, in which the AAF is external to the Z-DNA duplex.
ASJC Scopus subject areas