Identification of ester-linked fatty acids of bacterial endotoxins by negative ion fast atom bombardment mass spectrometry.
Negative ion fast atom bombardment mass spectrometry (NI-FAB/MS) was employed to characterize the fatty acids esterified to the lipid A backbone of lipopolysaccharides (LPS) of gram-negative bacteria. LPS and their chemically derived lipid A produced readily detectable fragment ions characteristic of fatty acids. The NI-FAB/MS method is specific, yielding ions indicative of ester- but not of amide-bound fatty acids. The mass spectra of Enterobacteriaceae LPS revealed the presence of lauric (m/z 199), myristic (m/z 227), palmitic (m/z 255), and 3-hydroxymyristic (m/z 243) acids. Pseudomonas aeruginosa LPS gave distinctive fragment ions indicative of 3-hydroxydecanoic (m/z 187), lauric, and 2-hydroxylauric (m/z 215) acids. The Neisseria gonorrhoeae LPS could be distinguished from the others due to the presence of ester-linked 3-hydroxylauric acid. All of the LPS gave abundant ions of m/z 177 and 159, which were derived from diphosphoryl substituents. The use of NI-FAB/MS thus allowed rapid identification of lipid A esterified fatty acids without chemical derivatization or gas chromatographic analysis.
D000577:Amides / Q000032:analysis; D002849:Chromatography, Gas; D004731:Endotoxins / Q000032:analysis*; D004952:Esters / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis*; D006090:Gram-Negative Bacteria / Q000032:analysis; D008050:Lipid A / Q000032:analysis; D008070:Lipopolysaccharides / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods
D000577:Amides; D004731:Endotoxins; D004952:Esters; D005227:Fatty Acids; D008050:Lipid A; D008070:Lipopolysaccharides