New Mass Spectrometric Methods for Peptidoglycan Analysis

Abstract

During the last two decades, mass spectrometry has encountered a series of dramatic advances in desorption/ionization techniques and experimental strategies which have improved its capability to characterize the structure of underivatized peptidoglycan monomers and oligomers. These techniques, collectively referred to as soft ionization methods, provide molecular weight and especially in combination with tandem mass spectrometer structural information for a wide range of polar and thermally labile compounds. Complementary information to the well established techniques such as two-dimensional nuclear magnetic resonance, gas-phase Edman degradation and amino sugar analysis can be obtained. One of these important improvements was the introduction of fast atom bombardment combined with a four-sector tandem mass spectrometer for the analysis of non-reduced peptidoglycan monomers by Martin et al. (1987). Recently, several other new desorption/ionization techniques have been applied to the characterization of large, thermally labile biomolecules. Cf-252 plasma desorption (PD), matrix assisted laser desorption (MALD) time-of-flight mass spectrometry and electrospray (ESI) mass spectrometry are important new techniques. All offer relative ease of sample preparation, high sensitivity, accurate molecular weight determination and the possibility to analyze molecules with molecular masses to 50 kDa and beyond. This paper offers a comparison of the performance of the last three techniques when applied to the direct analysis of reduced peptidoglycan monomers and oligomers and the extent of information which may be acquired.