title: Sensitivity of hydrogen bonds of DNA and RNA to hydration, as gauged by 1JNH measurements in ethanol-water mixtures.
abstract: Hydrogen-bond lengths of nucleic acids are (1) longer in DNA than in RNA, and (2) sequence dependent. The physicochemical basis for these variations in hydrogen-bond lengths is unknown, however. Here, the notion that hydration plays a significant role in nucleic acid hydrogen-bond lengths is tested. Watson-Crick N1...N3 hydrogen-bond lengths of several DNA and RNA duplexes are gauged using imino 1J(NH) measurements, and ethanol is used as a cosolvent to lower water activity. We find that 1J(NH) values of DNA and RNA become less negative with added ethanol, which suggests that mild dehydration reduces hydrogen-bond lengths even as the overall thermal stabilities of these duplexes decrease. The 1J(NH) of DNA are increased in 8 mol% ethanol to those of RNA in water, which suggests that the greater hydration of DNA plays a significant role in its longer hydrogen bonds. The data also suggest that ethanol-induced dehydration is greater for the more hydrated G:C base pairs and thereby results in greater hydrogen-bond shortening than for the less hydrated A:T/U base pairs of DNA and RNA.
authors.affiliation: Department of Biochemistry & Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA.
authors.forename: Marlon N
authors.initials: MN
authors.lastname: Manalo
authors.forename: Xiangming
authors.initials: X
authors.lastname: Kong
authors.forename: Andy
authors.initials: A
authors.lastname: LiWang
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D012313:RNA / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D000431:Ethanol; D012313:RNA; D004247:DNA