title: Theoretical studies of DNA-RNA hybrid conformations.
abstract: Molecular modelling has been used to probe the conformational preferences of double stranded DNA-RNA hybrids. As might be expected, the sugars of the DNA strand have higher conformational flexibility, but, for the majority of the repetitive sequences studied, these sugars prefer a C2-endo pucker, while ribose sugars uniformly adopt a C3-endo pucker. This gives rise to a strongly heteronomous duplex conformation. One exception to this rule involves the thymidine strand of poly(dT).poly(rA), which marginally prefers a C3-endo pucker. Our study further indicates that the DNA strands of the hybrids favour backbone torsions in the canonical B domain, rather than the modified values proposed on the basis of fibre diffraction studies. Backbone conformational transitions can nevertheless be induced leading to an alpha gamma-flip (alpha:gamma, g-/g(+)-->t/t) or to the alpha beta gamma-flip form proposed from fibre studies (alpha:beta:gamma, g-/t/g(+)-->t/g+/t). The latter transition is also found to be linked to BI-->BII transitions (epsilon:zeta, t/g(-)-->g-/t).
authors.affiliation: Laboratoire de Biochimie Théorique, CNRS URA 77, Institut de Biologie Physico-Chimique, Paris, France.
authors.forename: S R
authors.initials: SR
authors.lastname: Sanghani
authors.forename: R
authors.initials: R
authors.lastname: Lavery
mesh_terms: D000465:Algorithms; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D012313:RNA / Q000737:chemistry*
chemical_list: D012313:RNA; D004247:DNA