Elucidation of the O-specific polysaccharide chain of lipopolysaccharide (LPS) from Rickettsia typhi, the etiological agent of endemic typhus, is described. Structural information was established by a combination of monosaccharide and methylation analyses of the O-chain, and by mass (MS) and nuclear magnetic resonance (NMR) spectrometries of oligosaccharides arised through its hydrofluoric (HF) acid degradation. Based on the combined data from these experiments, two major polymer populations of the O-specific chain have been determined with the following structural features: α-L-QuiNAc-(1→4)-[α-D-Glc-(1→3)-α-L-QuiNAc-(1→4)]n-α-D-Glc- (1→4)-α-D-Glc→, α-D-Glc-(1→3)-α-L-QuiNAc-(1→4)-[α-D-Glc-(1→3)-α-L-QuiNAc-(1→4)]n-α-D-Glc→. The linear backbone is most probably flanked with short side chains of D-GlcNAc-(1→3)-α-L-QuiNAc-(1→3)-D-GlcNAc→ that are attached to it via L-QuiNAc as a branching point. It is suggested that a dimer α-L-QuiNAc-(1→3)-α-D-GlcNAc may represent a common epitope in the O-antigens of Proteus vulgaris OX19 and R. typhi responsible for the observed serological cross-reactivity.

Lipopolysaccharide, structure, O-antigens, chemical composition, Rickettsia typhi

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3	aDGlcp	100.1	72.5	72.5	77.8	72.5	60.9
2	Ac	?	22.0
	aLQuipN	98.3	54.6	79.4	75.0	69.3	17.5


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3	aDGlcp	5.01	3.45	3.45	3.50	3.45	3.60-3.71
2	Ac	-	2.00
	aLQuipN	4.84	4.09	3.72	3.27	4.07	1.22


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3	aDGlcp	100.1/5.01	72.5/3.45	72.5/3.45	77.8/3.50	72.5/3.45	60.9/3.60-3.71
2	Ac		22.0/2.00
	aLQuipN	98.3/4.84	54.6/4.09	79.4/3.72	75.0/3.27	69.3/4.07	17.5/1.22

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@@H](CO)O[C@H](O[C@@H]2[C@@H](O)[C@H](C)O[C@@H](*)[C@H]2NC(C)=O)[C@H](O)[C@H]1O

349.336 g/mol (C₁₄H₂₃R₂NO₉, R = next and previous repeats, not counted in mol weight)