[Possible DNA conformations].

The complete analysis of possible DNA structures has been undertaken in the space of dihedral angles. The structural sets obtained join energetically and geometrically possible conformations. Thus, the necessary condtions of existence are fulfilled for these structural forms. The half of our structural families includes all structures and structural sets proposed by other authors [10, 24]. Other six families have not been presented elsewhere. The results of the energy optimization suggest the left handed forms are unfavourable energetically, because main chain torsional term and the energy of nucleotide moiety. At the same time there is a great number of various lefthanded forms.