Computational screening of protein candidates. Spectra fingerprints were analyzed by MASCOT, comparing the experimental peaks against those obtained in silico from sequence databases. URFs were derived from planarian genome traces. Small triangles correspond to peptides found by MASCOT, mapped on candidate protein sequences for both databases, RefSeqs and URFs. Due to the size of the URFs database, a decoy approach was taken to select significant protein sequences. Putative protein sequences were ranked prior to experimental validation, taking into account MASCOT scores, number of peptide hits per sequence, decoy score, as well as functional assignment by BLAST2GO.