N‐acylsuccinimides as Acylating Agents for Proteins: The Selective Acylation of Lysine Residues

The suitability of N‐acylsuccinimides as reagents for the selective acylation of reactive side chains in proteins has been examined. A detailed study of the reaction of N‐acetylsuccinimide with ribonuclease and bovine serum albumin showed that acetylation occurred in the pH range 3 to 8. Lysine side chains were acetylated selectively, with little or no modification of tyrosine side chains. There was no evidence for acetylation of serine, threonine or histidine side chains. The analogous N‐propionyl, N‐n‐butyryl, N‐i‐butyryl and N‐n‐valerylsuccinimides also selectively acylate lysine side chains in proteins. This series of reagents, capable of changing the charge of lysine side chains and adding acyl groups of increasing hydrocarbon chain length, should prove a useful tool in studies of protein structure.