Trypsin autolysis fragments and matrix clusters are often observed as intense peaks in mass spectra of protein digests. It is demonstrated that these can be exploited to improve the mass calibration of a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectrometer. Interpretation of some of the autolysis masses is complicated by the existence of disulfide bonds. Surprisingly large matrix clusters are often visible for alpha-cyano-4-hydroxy-cinnamic acid. The fractional part of their masses differentiates them from protein digestion fragments.
Copyright 2002 John Wiley & Sons, Ltd.