title: Structural and thermodynamic studies on the adenine.guanine mismatch in B-DNA.
abstract: The structure of the synthetic dodecamer d(CGCAAATTGGCG) has been shown by single crystal X-ray diffraction methods to be that of a B-DNA helix containing two A(anti).G(syn) base pairs. The refinement, based on data to a resolution of 2.25 A shows that the mismatch base pairs are held together by two hydrogen bonds. The syn-conformation of the guanine base of the mismatch is stabilised by hydrogen bonding to a network of solvent molecules in both the major and minor grooves. A pH-dependent ultraviolet melting study indicates that the duplex is stabilised by protonation, suggesting that the bases of the A.G mispair are present in their most common tautomeric forms and that the N(1)-atom of adenine is protonated. The structure refinement shows that there is some disorder in the sugar-phosphate backbone.
authors.affiliation: Department of Chemistry, University of Edinburgh, UK.
authors.forename: G A
authors.initials: GA
authors.lastname: Leonard
authors.forename: E D
authors.initials: ED
authors.lastname: Booth
authors.forename: T
authors.initials: T
authors.lastname: Brown
mesh_terms: D000225:Adenine / Q000737:chemistry*; D001482:Base Composition; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D012997:Solvents; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D012997:Solvents; D006147:Guanine; D004247:DNA; D000225:Adenine