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.Today the methods of tandem mass spectrometry have aroused considerable interest among investigators throughout the world. They have been used not only to determine the molecular mass of an investigated sample but also to study the various mechanisms of intermolecular reactions.In spite of this on account of the increased complexity of the interpretation of the results due attention as not been paid to investigation of the ionization of high-molecular natural compounds.A special position among contemporary methods of mass-spectrometric analysis is occupied by matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI TOF MS). The method is maybe very young. It was proposed in 1988It was proposed in -1989, where UV-laser desorption was first used for the analysis of bioorganic compounds with molecular masses of more than 10 kDa.The main application of MALDI-TOF mass spectrometry is in the field of proteomics, the aim of which is the study of protein structure.The majority of the proteins taking part in particularly important biochemical processes are glycosylated, and analysis of their post-translational modification is also an extremely important aspect of proteomic investigations. Of particular interest are the proteases -enzymes that catalyze the selective cleavage of a protein chain and thereby regulate vitally important 0040-5760/08/4402-0075
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