Monitoring of Carboxypeptidase Digestion by Matrix-Assisted Laser Desorption and Ionization Mass Spectrometry

The potential of matrix-assisted laser desorption and ionization mass spectrometry (LDI-MS) is demonstrated by monitoring and analyzing the digestion of (human) pTH (1–34), a synthetic peptide with carboxypeptidases Y and B. All occurring ion signals in the mass spectra could be identified as degraded peptides. By calculating the mass differences between successive degraded peptides, it was possible to identify the released amino acids and to determine 8 amino acids of the C-terminus of the original peptide. For a single MS measurement, only 2 pmol of substrate was needed. Time-course analysis of the cleavage of the first amino acid residue gave insight into the kinetics involved. These measurements strongly support the hope that quantitative information about concentrations can be extracted from LDI-MS

Matrix-Assisted Laser Desorption and Ionization Mass Spectrometry and Its Applications in Chemistry

The present paper gives a summary of the potentialities of matrix-assisted laser desorption and ionization mass spectrometry (LDI-MS). Mass spectrometric information on different chemical and biochemical species are obtained with LDI-MS. Sulfonic acids, polysaccharides, oligonucleotides, and peptides were measured as negatively or positively charged ions in a time-of-flight mass spectrometer (TOF-MS). The amount of sample for a measurement lies between 50 pmol and 100 fmol and is, thus, comparable with other analytical and mass spectrometric methods. The large mass range from 0.6 kDa up to 200 kDa is accessible with LDI-MS. Molecular-weight determination can be done with an accuracy of less than 0.2%. Comparison with RP HPLC reveals the power of LDI-MS as an analytical tool