Fingerprinting of proteins cleaved in solution by cyanogen bromide

This paper describes a simple method for fingerprinting proteins cleaved in solution with cyanogen bromide (CNBr). Two modifications of standard solution CNBr digestion conditions facilitate routine application of solution digestion to multiple samples. First, proteins are recovered by neutralizing formic acid with N-ethylmorpholine and precipitating with acetone. This eliminates the need for lyophilization. Second, thiols are blocked by disulfide interchange. Disulfide interchange is simpler than reduction-alkylation because the reagent is inert and the excess need not be removed. We show how CNBr fingerprints of bovine serum albumin can be interpreted in terms of the amino acid sequence in ways that proteolytic fingerprints cannot.