Conformational and structural constraints in double‐helical polynucleotides

Conformational analysis of antiparallel double‐helical polynucleotides with Watson‐Crick base pairing was reduced to a four‐dimensional problem using original mathematical methods. In the four‐dimensional conformational space the family of structures, characterized by the base‐pair stacking with the most stable conformations in water solution as well as in the solid state, was localized. For the C′2‐endo sugar pucker, both right‐handed and left‐handed structures were found; right‐handed structures only, however, seem to be allowed for the C′3‐endo pucker, the only possible one for ribonucleotides with base stacking.