[Parallel double DNA spiral. A conformational analysis of regular spirals of poly(dA).poly(dT) with different variations of joining bases].

We have performed a conformational analysis of DNA double helices poly(dA).poly(dT) with parallel directed backbone strands in heteronomic model frames. All possible models of base pairs and various mutual orientation of base pair and sugarphosphate backbones were checked. By the potential energy optimization the dihedral angles and helices parameters of stable conformations of parallel double polynucleotides were calculated. The dependences of conformational energy on the base pair structure were studied.