The gram-negative bacterium Acinetobacter baumannii strain ATCC17961 has been used by several laboratories in mouse models of respiratory A. baumannii infection, and a study of the role of its lipopolysaccharide in the pathogenicity is of interest. The structure of the O-deacylated polysaccharide O-chain component of its LPS has been determined by 2D NMR spectroscopy and mass spectrometry methods, and by the structural identification of oligosaccharides obtained by sequential application of the Smith degradation of the O-antigen. The O-chain was determined to be a polymer of a branched pentasaccharide repeating unit composed of 2,3-diacetamido-2,3-dideoxy-d-glucuronic acid, 2-acetamido-2-deoxy-d-glucose, 2-acetamido-2-deoxy-d-galactose, d-glucose, and d-galactose, and has the following structure: (see text).

Lipopolysaccharide, NMR, LPS, structure, polysaccharide, O-antigen, Acinetobacter, Baumannii

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
4,2	Ac	176.3	23.2
4,3	Ac	176.3	23.2
4	bDGlcpN3NA	103.3	55.1	56.1	71.3	77.5	176.7
	bDGal?	97.7	73.3	73.9	76.8	75.3	61.5


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
4,2	Ac	-	2.01
4,3	Ac	-	2.01
4	bDGlcpN3NA	4.83	3.82	4.01	3.63	3.85	-
	bDGal?	4.57	3.35	3.75	4.11	3.70	3.68-3.80


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
4,2	Ac		23.2/2.01
4,3	Ac		23.2/2.01
4	bDGlcpN3NA	103.3/4.83	55.1/3.82	56.1/4.01	71.3/3.63	77.5/3.85	
	bDGal?	97.7/4.57	73.3/3.35	73.9/3.75	76.8/4.11	75.3/3.70	61.5/3.68-3.80

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

438.386 g/mol (C₁₆H₂₆N₂O₁₂)