High-performance liquid chromatographic mass spectrometric examination ofC-methylation artifacts from the permethylation reaction of peptides

Abstract

Combined high performance liquid chromatography mass spectrometry using a moving belt interface was used to investigate C-methylation artifacts arising from the permethylation reaction of peptides with methyl sulfinyl carbanion and methyl iodide. C-Methylation was not limited to glycine but, depending on the reaction conditions, other amino acids were also susceptible to it. In the absence of a glycine residue, preference for C-methylation of the C-terminus amino acid was observed. The use of on-line high performance liquid chromatography mass spectrometry allowed the separation of N, O, C-methylated from the N, O, S-permethylated derivatives, thus facilitating interpretation of the mass spectra.