Theoretical peptide length distributions produced from various cleavage agents. (a) Size frequency distributions (density) of peptides from proteome digestion by five real cleavage agents (i.e., trypsin, LysC, GluC, CNBr, and NTCB) and one theoretical cleavage agent (LeuC). The vertical black lines at 7 and 35 indicate general peptide identification size limits. (b) The same distribution focused on the region from 1 to 10 amino acids. (c) The view focused on the region between 30 and 40 amino acids.