Lipopolysaccharides (LPS), 3 also referred to as endotoxins, are an integral part of the outer membrane of Electrophoretic methods have been developed for gram-negative bacteria and are thus involved in the inthe analysis of complex carbohydrates derived from teraction of the cell with its environment. These complex lipooligosaccharides (LOS) of Moraxella catarrhalis membrane components are considered essential for the using capillary electrophoresis coupled to electronormal maintenance, growth, and reproduction of the spray mass spectrometry (CE-ESMS). Separation of cell (1). In addition, LPS are the main surface antigens lipooligosaccharides (LOS) arising from mild hydraziof gram-negative bacteria, and can lead to an immunonolysis of the intact lipopolysaccharides (LPS) was logical response from the host immune system through achieved using aqueous ammonium formate, and enthe stimulation of specific antibodies directed predomiabled identification of sites of heterogeneity (phosnantly against determinant structures of the LPS.
phates, phosphoethanolamine, and pendant acyl
The structure of LPS mainly consists of three distinct groups) on either the lipid A or the core oligosaccharegions: the O-specific chain, the core, and the lipid A.
ride. More complex mixtures of carbohydrates obtained from the complete deacylation and dephosphor-The O-specific chains contain the immunodeterminant ylation of LOS were amenable to electrophoretic structures against which the antibodies formed during conditions using both anionic and cationic separation. infection or immunization are directed (2, 3). Both the In particular, electrophoretic conditions were devel-O-specific chains and the core are comprised of long oped which permitted resolution of closely related olicarbohydrate chains, whereas the lipid A is formed of gosaccharides according to the number of carbohyfatty acid, phosphate, and phosphoethanolamine subdrate residues appended to the core structure. stituents bounded to a central glucosamine disaccha-Structural characterization of carbohydrates and LOS ride (1). It is noteworthy that the lipid A is also responreleased from the hydrazinolysis and acid hydrolysis sible for inducing the so-called endotoxic reactions in treatment of the intact LPS was achieved using tana host organism (4-8). In a large number of bacteria, dem mass spectrometry (MS-MS) for samples introthe lipid A and the core are linked together through duced by direct flow injection. Taken together, the one or more acidic carbohydrates such as 3-deoxy-Dcombination of CE-ESI-MS and MS-MS analyses promanno-2-octulosonic acid (KDO). The relatively labile vided valuable information on the heterogeneity of the LOS population in which a significant level of variability was found mostly in the lipid A portion.