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Structural investigation by tandem mass spectrometry analysis of a heterogeneous mixture of Lipid A n isolated from the lipopolysaccharide of Aeromonas hydrophila SJ‐55Ra
Author(s) -
Almostafa Mervt,
Fridgen Travis D.,
Banoub Joseph H.
Publication year - 2018
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.8017
Subject(s) - chemistry , lipid a , tandem mass spectrometry , disaccharide , mass spectrometry , electrospray ionization , chromatography , aeromonas hydrophila , lipopolysaccharide , bacteria , stereochemistry , medicine , endocrinology , biology , genetics
Rationale We report herein the electrospray ionization mass spectrometry (ESI‐MS) negative ion mode and low‐energy collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) analysis of a mixture of lipid A n isolated from the lipopolysaccharide (LPS) of a rough‐resistant wild strain of the Gram‐negative bacteria Aeromonas hydrophila grown in the presence of phages (SJ‐55Ra). This investigation indicates that the presence of a mixture of lipid A acylated disaccharides, whose molecular structures were not relatively conserved, resulted from the incomplete LPS biosynthesis caused by the phage treatment. Methods The heterogeneous lipid A n mixture from the LPS‐SJ55Ra was obtained following growth of the Gram‐negative bacteria Aeromonas hydrophila (SJ‐55R) in the presence of phages and isolation by the aqueous phenol method. Following hydrolysis and purification of the lipopolysaccharide, ESI‐MS and low‐energy CID‐MS/MS analyses were performed on a triple‐quadrupole (QqQ) and a Fourier transform ion cyclotron resonance (FTICR) instrument. Results ESI‐MS analysis suggested that this lipid A n mixture contained eight molecular disaccharide anions and three monosaccharide anions. This series of lipid A n was asymmetrically substituted with ((R)‐14:0(3‐OH)) fatty acids located at O‐3 and N‐2 and with branched fatty acids: (Cl4:0(3‐(R)‐ O ‐C14:0)) and (C12:0(3‐(R)‐ O ‐(14:0)) at the O‐3′ and N‐2′ positions. Conclusions Tandem mass spectrometric analyses allowed the exact determination of the fatty acid acylation locations on the D‐Glc p N disaccharide. The MS/MS results established that it was possible to selectively cleave C–O, C–N, and C–C bonds, together with glycosidic C–O and cross‐ring cleavages, affording excellent structural analysis of lipid A biomolecules.