Behavior of serine proteases thrombin, trypsin, and chymotrypsin under conditions of MALDI-TOF-Mass spectrometry

Features of ion formation under the influence of laser emission under the conditions of MALDI-TOF mass spectrometry in the glycosylated protein thrombin and the related proteases trypsin and chymotrypsin were studied for the first time. It was shown that trypsin and chymotrypsin are ionized in the form of molecular ions with masses 23800 and 25660 Da respectively. The molecular ion of thrombin was not detected; three main fragment ions with masses 9951, 10230, and 11982 Da were detected in the mass spectrum of thrombin. It was suggested that these fragments relate to peptide and glycopeptides fragment ions formed as a result of bond cleavage in the region of Asn60G during exposure to laser emission under the conditions of MALDI-TOF mass spectrometry.