Lipopolysaccharide (LPS) isolated from Escherichia coli D31m4, a heptoseless mutant, was studied by 13C and 31P NMR spectroscopy. Modified isolation and purification procedures are described which permitted high resolution NMR spectra to be obtained from samples of intact LPS. 31P NMR was used to monitor the purity and native heterogeneity of LPS samples. The anomeric carbon region of the 13C NMR spectrum taken at pH 7 contained five resonances that were assigned on the basis of chemical shift correlation, 13C-1H couplings, and T1 relaxation times. Two resonances, at 99.9 and 100.8 ppm, were attributed to two residues of 3-deoxy-D-manno-octulosonate (KDO) of which both were tentatively assigned to the α configuration. The Lipid A moiety gave rise to resonances at 94.0 and 94.9 ppm, both assigned to GlcN(I), and a resonance at 103.1 ppm, both assigned to glcN(II). The two anomeric carbon resonances observed for GlcN(I) reflected the variable substitution of C-1 with monophosphate or diphosphate groups. GlcN(I) and GlcN(II) were ascertained to be of the α and β anomeric configuration, respectively, through chemical shift comparisons with model saccharides. The accepted KDO linkage site at C-3' of GlcN(II) appears not to be supported by the 13C chemical shift data.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Biological Chemistry|
|State||Published - 1983|