Peptide characterization using bioreactive mass spectrometer probe tips

A method has been developed for the rapid and sensitive mass spectrometric characterization of peptides. The approach uses bioreactive mass spectrometer probe tips, incorporating covalently bound enzymes, which are capable of modifying biomolecules for analytical purposes. In the demonstrated cases, enzymatic proteolysis is initiated upon application of analyte to the probe tips, time is allowed for digestion, and the products are analyzed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. The probe tips have been used for proteolytic mapping and partial sequence determination of picomole quantities of peptide. Analysis times were approximately 30 min. Two methods of database search were utilized. The first used limited peptide sequence information and parent molecular weight, while the second used exclusively the molecular weights of a number of endoproteolytic fragments. A simple method of comparing the match of experimental data for a tryptic digest with the results of a search is described.