The NMR structural analyses of unmodified, intact Lipid X and Lipid A (endo
toxin) purified from wildtype Escherichia coli K-12 are described. Selectiv
e inverse decoupling difference spectroscopy (SIDDS) is introduced as a sim
ple and practical method for establishing phosphate linkage sites in Lipid
A and related compounds. Homo- and heteronuclear multi-dimensional correlat
ion NMR methods (COSY, TOCSY, HMQC, HMBC) were used in tandem to determine
acyl and phosphate attachment sites and to derive detailed H-1,C-13 and P-3
1 NMR assignments. The NOESY results confirm the beta-glycosidic linkage an
d chair conformations of the glucosamine rings in E. coli Lipid A. Copyrigh
t (C) 1999 John Wiley & Sons, Ltd.