FIG 2 .
MALDI-TOF MS analysis of lipid A isolated from five Bacteroides species. Lipid A was purified from B. thetaiotaomicron VPI 5482, B. fragilis NCTC 9343, B. ovatus ATCC 8343, B. uniformis ATCC 8492, and B. vulgatus ATCC 8482 by the TRI reagent method, dissolved in 3:1 chloroform-methanol, spotted on a 5-chloro-2-mercaptobenzothiazole (CMBT) matrix, and analyzed on a Waters Corporation Synapt G2 HDMS 32k MALDI-TOF instrument in reflectron negative-ion mode. All five have as their dominant lipid A species a cluster of peaks around 1,688 m/z corresponding to the published structure of B. thetaiotaomicron lipid A. The peaks in the cluster are separated by 14 m/z (methylene group, CH2), likely caused by heterogeneity in the number of carbons in each acyl chain of lipid A.