INTRODUCTIONThe sites of trypsin cleavage can be restricted when the ε-amino group of lysine is blocked, for example, by succinic anhydride. This can be useful for obtaining overlapping peptides during classical protein sequencing strategies. For example, in selective peptide cleavage with trypsin, it may be desirable to block the ε-amino groups of lysine so that the enzyme attacks only at arginine peptide bonds. Another advantage of succinylation is that the reagent places substantial negative charge on the protein because the positively charged lysine side chain is replaced by a negatively charged carboxyl group of the succinate half-amide. Hence, succinylation may be used to solubilize a protein while blocking its lysine groups (in general, succinylated proteins are soluble at pH >7). The attached succinyl moiety forms a stable linkage to most protein treatments, but may be cleaved off with 6 N HCl at 100ºC.