title: Switching binding sites: low-temperature NMR studies on adenosine-aspartic acid interactions.
abstract: Low-temperature NMR experiments were performed on mixtures of adenine nucleosides and aspartic acid derivatives in a freonic solvent. By acquiring spectra at temperatures as low as 123 K, the regime of slow hydrogen bond exchange is reached and hydrogen-bonded complexes can be characterized in detail. With 2'-deoxyadenosine lacking a 2'-substituent, N-Boc-protected aspartic acid benzyl ester binds through its carboxylic acid side chain to the Watson-Crick site of the adenine base, forming a strong hydrogen bond with the proton located close to the center between the oxygen donor and adenine N1 nitrogen acceptor. However, in the case of 2'-O-silylated adenine ribofuranosides, noncovalent interactions of the 2'-substituent with protecting groups on the amino acid shift the binding mode toward a Hoogsteen geometry with only a moderately strong hydrogen bond involving adenine N7.
authors.affiliation: Institut für Chemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany.
authors.forename: Eline M Basílio
authors.initials: EM
authors.lastname: Janke
authors.forename: Klaus
authors.initials: K
authors.lastname: Weisz
mesh_terms: D000241:Adenosine / Q000737:chemistry*; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000737:chemistry*; D001665:Binding Sites; D005617:Chlorofluorocarbons, Methane / Q000737:chemistry; D003903:Deuterium; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D013696:Temperature
chemical_list: D005617:Chlorofluorocarbons, Methane; D001224:Aspartic Acid; D003903:Deuterium; D000241:Adenosine