Drug-nucleic acid interactions: conformational flexibility at the intercalation site.

Abstract
Conformational features of the intercalation site in polynucleotides were examined. For all crystal structures of drug-dinucleoside complexes studied thus far, 2 torsion angles apparently differ from those found in A RNA (.vphi. and .chi., and alternate sugar puckering may not be prerequisite for intercalation. This intercalation geometry, which is the basis of helix axis displacement in a polymer, would necessitate conformational changes in adjacent nucleotides. The base-turn angle is less sensitive to conformation of the backbone than it is to small alterations in the base-pairing geometry. Apparently this angle is dependent on the nature of the intercalating drug.