Mapping bacterial glycolipid complexity using capillary electrophoresis and electrospray mass spectrometry

This chapter presents the application of capillary electrophoresis coupled to electrospray mass spectrometry (CE-ES-MS) for the analysis of complex bacterial lipopolysaccharides (LPS) from pathogenic strains of Haemophilus influenzae and Neisseria meningitidis. A discussion is included of the development of electrophoretic conditions conducive to trace-level enrichment and separation of closely related glycoforms and isoforms, which provided sensitive detection of glycolipids from as little as five bacterial colonies. The chapter also describes the use of mixed MS scanning functions to aid the identification of specific functionalities and immunodeterminants of LPS, such as pyrophosphoethanolamine, phosphocholine, and N-acetyl neuraminic acid (Neu5Ac), which represent less than 2% of the overall LPS population. The combination of high-resolution capillary electrophoresis with sensitive tandem mass spectrometry (MS/MS) provides a unique analytical tool to probe the subtle structural changes resulting from oligosaccharide branching and location of substituted LPS isoforms. The ability to detect a diverse LPS population over a wide dynamic range of expression using CE-MS enables the correlation of structural changes between bacterial strains and isogenic mutants to assign functional gene relationship.