title: Carbon-13 nuclear magnetic resonance studies of cobalamins.
abstract: The carbon-13 nuclear magnetic resonance spectra of aquocobalamin, adenosylcobalamin, methylcobalamin, and (carboxymethyl)cobalamin have been interpreted. The assignments were made by a comparison of the spectra with that of cyanocobalamin, by a study of the pH dependence of the chemical shifts, by an analysis of the effect of the axial ligands on the carbon atoms of the corrin ring, and by a study of the specific line broadening effect of the paramagnetic ions Mn2+ and Gd3+. The chemical shift changes that accompany the "base-on"----"base-off" conversion of the organocobalamins demonstrate that the conformation of the "western" half of the corrin ring and the conformations of the a, b, c, d, f, and g side chains are relatively constant. In contrast, the conformations of the "eastern" half of the corrin ring and the e propionamide side chain are highly variable.
mesh_terms: D002244:Carbon; D055598:Chemical Phenomena; D002621:Chemistry; D003038:Cobamides; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000494:pharmacology; D008968:Molecular Conformation; D009705:Nucleosides; D009711:Nucleotides; D014805:Vitamin B 12 / Q000031:analogs & derivatives
chemical_list: D003038:Cobamides; D009705:Nucleosides; D009711:Nucleotides; C043960:aquacobalamin; C043959:Co-(carboxymethyl)cobalamin; D008345:Manganese; D002244:Carbon; C019476:mecobalamin; C000913:cobamamide; D014805:Vitamin B 12