The mass spectrometric analysis produces a list of molecular weights of the fragments which is often called a peak list. The peptide masses are compared to protein databases such as Swissprot , which contain protein sequence information. Software performs in silico digests on proteins in the database with the same enzyme (. trypsin) used in the chemical cleavage reaction. The mass of these peptide fragments is then calculated and compared to the peak list of measured peptide masses. The results are statistically analyzed and possible matches are returned in a results table.