title: Assignment of cytosine N3 resonances in nucleic acids via intrabase three-bond coupling to amino protons.
abstract: Coherences were observed between 15N3 of cytosine and its trans amino proton (H42) using a modified gradient-based heteronuclear single quantum coherence (HSQC) pulse sequence optimized for three-bond proton-nitrogen couplings. The method is demonstrated with a 22-nucleotide RNA fragment of the P5abc region of a group I intron uniformly labeled with 15N. Use of intraresidue 15N3-amino proton couplings to assign cytosine 15N3 signals complements the recently proposed JNN HNN COSY [Dingley, A.J. and Grzesiek, S. (1998) J. Am. Chem. Soc., 120, 8293-8297] method of identifying hydrogen-bonded base pairs in RNA.
authors.affiliation: Department of Chemistry, University of California, Berkeley, USA.
authors.forename: S
authors.initials: S
authors.lastname: Rüdisser
authors.forename: J G
authors.initials: JG
authors.lastname: Pelton
authors.forename: I
authors.initials: I
authors.lastname: Tinoco
mesh_terms: D000818:Animals; D003596:Cytosine / Q000737:chemistry*; D006860:Hydrogen Bonding; D007438:Introns; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009587:Nitrogen Isotopes; D011522:Protons; D012313:RNA / Q000737:chemistry*; D016053:RNA, Protozoan / Q000737:chemistry; D016808:Tetrahymena thermophila / Q000235:genetics
chemical_list: D009587:Nitrogen Isotopes; D011522:Protons; D016053:RNA, Protozoan; D012313:RNA; D003596:Cytosine