Positive-ion fragmentation in matrix-assisted laser desorption/ionization tandem time of flight mass spectrometry of synthetic analogs of the O-specific polysaccharide of Vibrio cholerae O:1

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006

This review is the fourth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.

Negative matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry fragmentation of synthetic analogs of the O-specific polysaccharide of Vibrio cholerae O:1 in the presence of anionic dopants

Oligosaccharides (tri- to hexamers) that represent terminal epitopes of O-antigens of Vibrio cholerae O:1, serotypes Ogawa and Inaba, have been studied by negative matrix-assisted laser desorption/ionization time of flight/time-of-flight mass spectrometry (MALDI ToF/ToF MS). The [M - H(+)](-) ions are formed after expulsion of a proton from molecules studied under condition of MALDI MS analysis in the negative mode. Several ammonium salts (chloride, nitrate, hydrogencarbonate and hydrogensulfate) were used as additives to increase the formation of negative ions from saccharides. The most efficient was the addition of ammonium hydrogencarbonate, which increased the amount of [M - H(+)](-) ions more than six times. Between three fragmentation pathways, the new conjugated transfer of electrons within the second downstream unit of oligosaccharides was discovered. Production of these ions, which has not been observed in any other kinds of measurement, distinguishes substances belonging to Ogawa and Inaba serotypes. The negative MALDI ToF/ToF mass spectra are simpler and, at the same time, more informative, as compared with positive and negative electrospray ionization ion trap as well as with positive MALDI ToF/ToF analysis.