ALCOHOLYTIC DEBLOCKING OF N-TERMINALLY ACETYLATED PEPTIDES AND PROTEINS FOR SEQUENCE-ANALYSIS

N-terminal acetylation of polypeptides is a common feature preventing direct Edman degradation, We describe a method for the removal of the acetyl group, with only a low extent of internal peptide bond cleavage , also in large proteins, by treatment at room temperature with triflu oroacetic acid and methanol, The alcohol is essential for selective de acetylation, and it is proposed that the deblocking mechanism consists of an acid-catalyzed nucleophilic substitution involving methanol. Th e extent of deacetylation is limited, but the initial yield in the seq uence analysis can be up to 10%, Deblocking of samples spotted or blot ted onto sequencer filters is equally possible as the use of isolated samples from column separations. Deblocking on sequencer filters is al so possible directly after negative results on initial sequencer attem pts with samples proving to be blocked.