Selectivity of labeled bromoethylamine for protein alkylation.

Alkylation of cysteine residues has been used extensively for characterization of proteins and their mode of action in biological systems, research endeavors that are at the core of proteomics. Treatment with a simple alkylating agent such as [2-(13)C] bromoethylamine would result in labeled thialysine at the ε-position. This chemical modification of proteins would allow investigations via both (13)C NMR spectroscopy and mass spectrometry.