Proton nuclear magnetic resonance(1H-NMR) signal assignment of vitamin B12 based on normal two-dimensional NMR and feeding experiments.

Abstract

Proton nuclear magnetic resonance (1H-NMR) signal assignment of cyanocobalamin (vitamin B12) was achieved by the normal two-dimensional NMR method. 1H-1H correlation spectroscopy (COSY) of vitamin B12 showed correlation networks of dimethyl benzimidazole, ribose, isopropanolamine, and corrin ring proton peaks. 1H-1H nuclear Overhauser effect (NOE) spectroscopy (NOESY) allowed assignment of the benzimidazole protons. For assignment of methyl and methylene protons of the corrin ring, 1H-13C COSY measurements were made on 13C-enriched vitamin B12, isolated after feeding experiments with [13CH3]methionine, [2-13C]5-aminolevulinic acid (ALA), and [3-13C]ALA.