IVICAT for the masses: an improved technique for permethylation of peptides.

To determine the levels of post-translational modifications, we needed a quantitative technique that would allow comparison of the amounts of acetylated versus mono-, di-, and tri-methylated lysines in histones. One method, IVICAT, generates trimethyl-amines and could be used, but is technically challenging. We have modified this technique to be used with standard laboratory equipment so that this chemistry is accessible to most proteomics laboratories.