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Elucidation of the molecular structure of lipid A isolated from both a rough mutant and a wild strain of Aeromonas salmonicida lipopolysaccharides using electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry
Author(s) -
ElAneed Anas,
Banoub Joseph
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1971
Subject(s) - chemistry , disaccharide , aeromonas salmonicida , tandem mass spectrometry , electrospray ionization , lipid a , mass spectrometry , electrospray , stereochemistry , chromatography , bacteria , genetics , biology
The chemical structure of lipid A, isolated by mild acid hydrolysis from a rough mutant and a wild strain of Aeromonas salmonicida lipopolysaccharide, was investigated using electrospray ionization quadrupole time‐of‐flight (QqToF) hybrid tandem mass spectrometry and showed a great degree of microheterogeneity. The chemical structure of the main constituent of this heterogeneous mixture was identified as a β ‐D‐(1 → 6) linked D‐glucosamine disaccharide substituted by two phosphate groups, one being bound to the non‐reducing end at position O‐4′ and the other to the position O‐1 of the reducing end of the D‐glucosamine disaccharide. The location of the fatty acids linked to the disaccharide backbone was established by identifying diagnostic ions in the conventional QqToF‐MS scan. Low‐energy collision tandem mass spectrometry analysis of the selected precursor diagnostic ions confirmed, unambiguously, their proposed molecular structures. We have established that myristyloxylauric (C14:0(3‐ O (12:0))) acid residues were both N‐2′ and O‐3′ linked to the non‐reducing end of the D‐GlcN residue, and that two 3‐hydroxymyristic (C14:0(3‐OH)) acid chains acylated the remaining positions of the reducing end. The MS and MS/MS data obtained allowed us to determine the complex molecular structure of lipid A. The QqToF‐MS/MS instrument has shown excellent superiority over a conventional quadrupole‐hexapole‐quadrupole tandem instrument which failed to fragment the selected precursor ion. Copyright © 2005 John Wiley & Sons, Ltd.