title: A solid-state (17)O nuclear magnetic resonance study of nucleic acid bases.
abstract: We report a systematic solid-state (17)O NMR study of free nucleic acid bases: thymine (T), uracil (U), cytosine (C), and guanine (G). Site-specifically (17)O-enriched samples were synthesized:[2-(17)O]thymine (1), [4-(17)O]thymine (2), [2-(17)O]uracil (3), [4-(17)O]uracil (4), [2-(17)O]cytosine (5), and [6-(17)O]guanine monohydrate (6). Magic-angle-spinning (MAS) and static (17)O NMR spectra were acquired at 11.75 T for compounds 1-6, from which information about the (17)O chemical shift and electric field gradient tensors was obtained. Extensive quantum chemical calculations were performed at the B3LYP/6-311++G(d,p) level of theory for (17)O NMR properties in various molecular models. The calculated (17)O NMR tensors are highly sensitive to the description of intermolecular hydrogen-bonding interactions at the target oxygen atom. A reasonably good agreement between experimental solid-state (17)O NMR data and B3LYP/6-311++G(d,p) calculations is achievable only in molecular cluster models where a complete hydrogen-bond network is considered. Using this theoretical approach, we also investigated the (17)O NMR tensors in two unusual structures: guanine- and uracil-quartets.
authors.affiliation: Contribution from the Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6. gangwu@chem.queensu.ca
authors.forename: Gang
authors.initials: G
authors.lastname: Wu
authors.forename: Shuan
authors.initials: S
authors.lastname: Dong
authors.forename: Ramsey
authors.initials: R
authors.lastname: Ida
authors.forename: Nitin
authors.initials: N
authors.lastname: Reen
mesh_terms: D018360:Crystallography, X-Ray; D003596:Cytosine / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D007553:Isotope Labeling; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010103:Oxygen Isotopes; D013941:Thymine / Q000737:chemistry*; D014498:Uracil / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D014498:Uracil; D006147:Guanine; D003596:Cytosine; D013941:Thymine