Mass spectrometric strategy for the characterization of lipooligosaccharides from Neisseria gonorrhoeae 302 using FTICR

Abstract

The lipooligosaccharides (LOS) of Neisseria gonorrhoeae 302 were profiled using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Using techniques developed in this laboratory, the topology and some of the linkages of the LOS were determined. Mass spectrometric analysis in the negative ion mode yielded a glycoform of the composition: Hex 3 Hep 2 Hxn 1 PEA 1 KDO 2 DPLA. The composition was confirmed through exact mass measurements, which showed only a 2 ppm error between the exact mass and theoretical mass. Although the core structure has been postulated previously, the positioning of the three hexose moieties were in question for this particular strain of N. gonorrhoeae. Topology assignment was performed through collision-induced dissociation analysis of the O-deacylated glycoform in the negative ion mode followed by submission to the saccharide topology analysis tool (STAT) computer program, which confirmed the topology assignment. It was found that the three hexoses were added to the Hep[I] of the conserved core of N. gonorrhoeae in a linear fashion, while Hep[II] remains unbranched. Linkage position analysis was performed through application of a mild acid hydrolysis technique followed by collision-induced dissociation of the sodiated precursor ions, yielding a 1 → 4 linkage between the terminating and penultimate hexoses.