DERIVATIZATION OF BILE-ACIDS WITH TAURINE FOR ANALYSIS BY FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY WITH COLLISION-INDUCED FRAGMENTATION

When analyzed by fast atom bombardment mass spectrometry, taurine-conj ugated bile acids give intense [M-H]- pseudomolecular ions that can be subjected to collision-induced fragmentation to give structural infor mation. A method has been developed that permits rapid coupling of tau rine to unconjugated, glycine-conjugated, sulfated, and glucuronidated bile acids. The reaction is performed for 2 h at room temperature in aqueous pyridine hydrochloride buffer, with or without dioxane, using 0.1 M 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as the coupling a gent and 0.2 M taurine. The yields are higher than 95%. In contrast to published coupling reactions, the method permits conjugation of bile acids with the labile 7alpha-hydroxy-3-oxo-4-ene structure.