CHARACTERIZATION OF PEPTIDOGLYCAN TRIMERS AFTER GEL CHROMATOGRAPHY AND REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY BY POSITIVE-ION PLASMA DESORPTION MASS-SPECTROMETRY

A strategy for the primary structure characterization of reduced pepti doglycan trimers derived from muramidase-digested murein (e.g. isolate d from the cyanelles of Cyanophora paradoxa) is outlined. First, murop eptides are separated by gel filtration according to their size (degre e of cross-linking). This step is followed by reduction with sodium bo rohydride and reversed-phase high-performance liquid chromatography (H PLC). Trimeric and oligomeric compounds (molecular weight range 2500-4 500 Da), in particular, are present in small quantities and therefore sophisticated methods for characterization are required due to the bio logical importance of these components. For determining molecular weig ht with high accuracy, positive-ion plasma desorption mass spectrometr y (PDMS) proves to be a well-suited analytical method with sufficient sensitivity (medium picomole range) and mass accuracy (+/-0.04%). Base d on combined data from PDMS, gel chromatography, HPLC and amino acid and amino sugar analyses, the primary structure of peptidoglycan trime ric compounds could be determined unambiguously.