title: Incorporation of oxygen-18 into nucleosides and bases.
abstract: Extensive incorporation of oxygen-18 at position O4 of the pyrimidine nucleus results from exchange between H218O and nucleosides or bases in 1N HC1 at 100 degrees. The reaction is hindered by substitution at C-5 with the greatest effect shown in pseudouridine (R = ribosy1) and the least in uridine (R = H). Maximum incorporation in the latter compound was 94%, and in uricil was 98%. The method is experimentally simple and the incorporation is readily monitored by mass spectrometry.
mesh_terms: D007042:Hypoxanthines; D007553:Isotope Labeling; D013058:Mass Spectrometry; D010103:Oxygen Isotopes; D011744:Pyrimidinones; D013941:Thymine; D013997:Time Factors; D014498:Uracil; D014529:Uridine / Q000031:analogs & derivatives
chemical_list: D007042:Hypoxanthines; D010103:Oxygen Isotopes; D011744:Pyrimidinones; D014498:Uracil; D013941:Thymine; D014529:Uridine