title: 1H NMR studies on the conformational characteristics of 2-thiopyrimidine nucleotides found in transfer RNAs.
abstract: The molecular conformations of naturally occurring 2-thiopyrimidine nucleosides (5-methylaminomethyl-2-thiouridine, 5-methoxycarbonylmethyl-2-thiouridine and 2-thiocytidine) and 5'-mononucleotides (5-methylaminomethyl-2-thiouridine 5'-monophosphate and 2-thiocytidine 5'-monophosphate) in 2H2O solution were elucidated by analyses of the proton NMR spin-coupling constant, nuclear Overhauser effect, and lanthanide-induced shifts and relaxation enhancements. As monomers, these nucleotides are almost exclusively in the 3E-gg-anti form, even in the absence of ordinary stabilizing factors of this form; i. e., base-stacking and base-pairing interactions with other nucleotide units. This inherent conformational rigidity of the 2-thiopyrimidine units probably contributes to stability of the conformation of tRNA.
mesh_terms: D004926:Escherichia coli / Q000032:analysis; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009690:Nucleic Acid Conformation; D012343:RNA, Transfer; D012260:Ribonucleases; D013873:Thionucleotides / Q000032:analysis*
chemical_list: D046911:Macromolecular Substances; D013873:Thionucleotides; D012343:RNA, Transfer; D012260:Ribonucleases