Negative electrospray, ion trap multistage mass spectrometry of synthetic fragments of the O-PS of Vibrio cholerae O:1

Eur. J. Mass Spectrom. 12, 43–50 (2006)
DOI: 10.1255/ejms.790

Negative electrospray, ion trap multistage mass spectrometry of synthetic fragments of the O-PS of Vibrio cholerae O:1

Slávka Bekešová,^a,* Vladimír Kováčik,^a Josef Chmelík^b and Pavol Kováč^c
^aInstitute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia. E- mail: chembeke@savba.sk
^bInstitute of Analytical Chemistry, Czech Academy of Sciences, Veveří 97, 811 42 Brno, Czech Republic
^cNIDDK, National Institute of Health, Bethesda, Maryland 20892-0815, USA

ABSTRACT:

Saccharides (mono through hexasaccharides) that mimic the terminal epitopes of O-antigens of Vibrio cholerae O:1, serotypes Ogawa and Inaba, were studied by electrospray ion trap (ESI IT) mass spectrometry (MS) in the negative mode. Anionized adducts are the characteristic ions formed by the capture of H₃O₂^– under the condition of ESI MS analysis. The reactive species are produced by reaction of hydroxyl anions with the molecule of water. Thus the [M + H₃O₂]^– have the highest m/z value in the ESI IT negative mass spectra. After dissociation of adducts by loss of 2H₂O the [M – H]^– ions are produced. The fragmentation pathways were confirmed by multistage measurements (MSⁿ). The predominant pathway of fragmentation of the mono- and oligomers is the elimination of a molecule of α-hydroxy–γbutyrolactone from the 4-(3-deoxy-L-glycero-tetronamido) group. The other characteristic pathway occurs by shortening the length of oligosaccharides. In this way, conversion of the Ogawa to Inaba fragments takes place under the conditions of measurement. Negative ESI MS/MS provided sufficient information about molecular mass, the number of saccharide residues, basic structure of saccharides, about the tetronamide part of the compounds investigated and allowed Ogawa and Inaba serotypes to be distinguished.

Keywords: electrotrospray ionization, negative multistage ion trap mass spectra, synthetic fragments of the lipopolysaccharide of Vibrio cholerae O:1

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