Comparison of positively charged DNG with DNA duplexes: a computational approach.

Molecular dynamics is used to investigate the structural properties of the cationic DNA analogue deoxynucleic guanidine (DNG), in which a guanidinium group replaces the phosphate moiety of DNA. This study examines the DNG duplex dodecamers d(Ag)(12).d(Tg)(12) and d(Gg)(12).d(Cg)(12), as well as their DNA counterparts. Watson-Crick base-pairing is maintained in the solvated DNG duplex models during the 5ns simulations. The idealized DNG dodecamers assume many parameters characteristic of the corresponding native DNA, assuming B-DNA conformations. Several helical parameters are rather unique to DNG, including buckle, slide, inclination, propeller, and X-displacement. Fewer transitions in backbone torsions occur in the DNG duplexes compared to those of the DNA, which may result from the greater rigidity of the sp(2) hybridized guanidinium group verses the flexible sp(3) phosphate group. The DNG helices have exceptionally shallow major grooves and very deep minor grooves. The major and minor groove widths of DNG are narrower than those of the respective DNA counterparts.