STRUCTURAL CHARACTERIZATION OF PEPTIDOGLYCAN MUROPEPTIDES BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY AND POSTSOURCE DECAY ANALYSIS

In this study we report the development of matrix-assisted laser desor ption ionization mass spectrometry (MALDI-MS)-based methods for the st ructural characterization of muropeptides derived from peptidoglycan. prior to analysis, peptidoglycan samples were subjected to enzymatic d igestion with muramidase and the resulting muropeptides mere purified by HPLC. A new matrix, 5-chloro-2-mercaptobenzothiazole, was employed for the MALDI-MS analysis. The results have demonstrated that sub-pico mole to femtomole detection can be achieved in both positive mode and negative mode, allowing unambiguous determination of the molecular mas ses of monomeric and oligomeric muropeptides. Structural information f rom monomeric muropeptides was obtained by further postsource decay (P SD) analysis. Fragmentation patterns in positive mode and negative mod e PSD were complementary for the elucidation of the peptide chain sequ ence. Lysostaphin digestion was also incorporated with MALDI mass mapp ing analysis for determination of peptide chain cross-linking patterns of muropeptide oligomers from Staphylococcus aureus strains. (C) 1997 Academic Press.