Chemical cleavage at aspartyl residues for protein identification

An alternative method to enzymatic digestion for protein identification by mass spectrometry has been developed that is based on chemical cleavage by formic acid. This method was tested on gel-purified apomyoglobin and BSA, a s well as unknown proteins that cofractionate with Ty1-virus-like particles from Saccharomyces cerevisiae. Cleavage at aspartyl residues was found to be efficient and specific, and this specificity of cleavage lent itself eas ily to database searches. Parallel digestions using trypsin were also perfo rmed. The formic acid cleavage method generated comparable or better result s than tryptic digestion for protein identification.