Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of Lipopolysaccharides

The outer membrane of Gram-negative bacteria, which include many human pathogens, contains various proteins, polysaccharides, and glycolipids. Of these, lipopolysaccharides (LPS) are of particular microbiological, immuno-logical, and medical importance. As the major amphiphilic components of the outer leaflet of the outer membrane, LPS fulfill a vital role for the organization and function of the outer membrane (e.g., effective permeation barrier to harmful substances). Furthermore, LPS represent the main surface antigen (O-anti-gen) harboring binding sites for antibodies and are thus involved in the specific recognition by the host organism’s defense system. When released from bacteria, for example, during multiplication, death, or lysis, LPS induce in mammalis a broad spectrum of physiological and pathological activities such as stimulation of cytokine production and act as potent bacterial toxins responsible for the toxic manifestation of Gram-negative infections (e.g., septic shock). To emphasize these activities LPS have also been termed endotoxins .