Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9744930 | Analytical Biochemistry | 2005 | 14 Pages |
Abstract
Lipid A isolated by mild acid hydrolysis from lipopolysaccharides of 22 nontypeable and 2 type f Haemophilus influenzae strains was investigated using electrospray ionization coupled to quadrupole ion trap mass spectrometry. The lengths, positions, and number of acyl chains in the lipid A molecule were determined using multiple-step tandem mass spectrometry (MSn). All of the analyzed strains showed a major lipid A molecule comprising β-2-amino-2-deoxy-d-glucopyranose-(1 â 6)-α-2-amino-2-deoxy-d-glucopyranose phosphorylated at the C4â² and C1 positions. The C2/C2â² and C3/C3â² positions were substituted by amide-linked and ester-linked 3-hydroxytetradecanoic acid chains, respectively. The fatty acid chains on C3â² and C2â² were further esterified by tetradecanoic acid chains. In all strains, minor amounts of lipid A molecules with different acylation patterns were identified. Thus, structures comprising the hexaacylated lipid A with the C2 or C3 position being substituted by 3-hydroxydecanoic acid, and hexaacylated lipid A with the C3 and C3â² positions being substituted by 3-hydroxydodecanoic or dodecanoyloxytetradecanoic acid, respectively, were found. In addition, lipid A with an acetyl group attached to the 3-hydroxytetradecanoic acid groups attached to the C2 or C3 position was detected in two nontypeable H. influenzae strains.
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Authors
Ivan Mikhail, HÃ¥kan H. Yildirim, Emma C.H. Lindahl, Elke K.H. Schweda,