Top-Down Characterization of Bacterial Lipopolysaccharides and Lipooligosaccharides Using Activated-Electron Photodetachment Mass Spectrometry

• Published in: Analytical chemistry (Washington) 2024-06, Vol.96 (22), p.9151-9158
• Main Authors: Keener, James E., Goh, Byoungsook, Yoo, Ji-Sun, Oh, Sungwhan F., Brodbelt, Jennifer S.
• Format: Article
• Language: English
• Subjects: Bacteroides fragilis - chemistry; Electrons; Escherichia coli - chemistry; Lipopolysaccharides - chemistry; Tandem Mass Spectrometry
• ISSN: 0003-2700; 1520-6882; 1520-6882
• DOI: 10.1021/acs.analchem.4c00952

Lipopolysaccharides (LPS) and lipooligosaccharides (LOS) are located in the outer membrane of Gram-negative bacteria and are comprised of three distinctive parts: lipid A, core oligosaccharide (OS), and O-antigen. The structure of each region influences bacterial stability, toxicity, and pathogenesis. Here, we highlight the use of targeted activated-electron photodetachment (a-EPD) tandem mass spectrometry to characterize LPS and LOS from two crucial players in the human gut microbiota, Escherichia coli Nissle and Bacteroides fragilis. a-EPD is a hybrid activation method that uses ultraviolet photoirradiation to generate charge-reduced radical ions followed by collisional activation to produce informative fragmentation patterns. We benchmark the a-EPD method for top-down characterization of triacyl LOS from E. coli R2, then focus on characterization of LPS from E. coli Nissle and B. fragilis. Notably, a-EPD affords extensive fragmentation throughout the backbone of the core OS and O-antigen regions of LPS from E. coli Nissle. This hybrid approach facilitated the elucidation of structural details for LPS from B. fragilis, revealing a putative hexuronic acid (HexA) conjugated to lipid A.