PARALLEL DNA HELICES - CONFORMATIONAL-ANALYSIS OF REGULAR POLY(DG) . POLY(DC) HELICES WITH DIFFERENT BASE-PAIRING TYPES

The results of conformational analysis of homopolymeric double helices of poly(dG) . poly(dG) . poly(dC) DNA with parallel orientation of th e sugar-phosphate backbones are presented for all possible types of ba se pairing. The dihedral angles of sugar-phosphate chains and the para meters corresponding to minimal conformational energy of the DNA helix were determined from the results of optimizing the potential energy c alculated by the method of atom-atom potentials. Analysis was carried out for the dependence of the conformational energy on the type of bas e hydrogen bonding and on the direction of the sugar-phosphate chains. The possible structure of parallel DNA helices with different nucleot ide composition is discussed.