Protein fingerprinting by SDS-gel electrophoresis after partial fragmentation with CNBr

The CNBr fragmentation reaction was adapted for the degradation of microgram quantities of protein in sodium dodecyl sulfate gel bands. These bands are then electrophoresed so as to generate easily distinguishable protein fingerprints. The method was tested on three proteins of known sequence and shown to generate nearly the full range of possible peptide fragments. It was also employed to compare the structures of several yeast aminoacyl tRNA synthetases and a contaminating crystallizable protein.