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item Price, Neil

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2006
Publication Date: 7/4/2006
Citation: Price, N.P. 2006. Oligosaccharide structures studied by hydrogen-deuterium exchange (HX) and MALDI-TOF mass spectrometry. Analytical Chemistry. 78(15):5302-5308.

Interpretive Summary: A full understanding of the way that sugars are metabolized or how they fold and bind to other molecules requires detailed knowledge of their chemical composition. Mass spectrometry is increasingly used to chemically identify sugars because it is rapid and often gives characteristic exact molecular weights. Larger sugars or sugar-protein complexes tend to degrade under these conditions so that only the weights of the fragments arising are seen. This report describes a new and more accurate method for characterizing large sugars. The method is based on the increase in mass observed when the exchangeable hydrogens on sugars are replaced with deuterium. This greatly increases confidence in their characterization, and may also be an approach to understanding how sugars bind to other biological molecules. The method has been used for several carbohydrates of potential agricultural importance. Without further work, it is of interest mainly to scientists engaged in the characterization of carbohydrates and sugars.

Technical Abstract: Hydrogen-deuterium exchange matrix-assisted laser desorption/ionization - time-of-flight mass spectrometry (HX-MALDI-TOF MS) is reported for the first time for the determination of exchangeable protons in diverse oligosaccharide and glycoconjugate structures. The method is generally analogous to the well-established amide proton exchange technique for proteins, and has broad application for determining carbohydrate structure and conformation, and to the study of carbohydrate-ligand interactions. The HX process has been optimized to give complete proton exchange and to minimize the well known problem of back-exchange. The optimized HX-MALDI-TOF MS technique is suitable for the analysis of all exchangeable proton types in carbohydrates. This has been validated for several diverse carbohydrate structures, including series of malto- and xylopyranose oligosaccharides; alpha- and beta-cyclodextrins; a non-reducing tetrasaccharide, stachyose; an N-acetylamide-containing oligosaccharide, chitotetraose; a tertiary hydroxyl-containing antibiotic glycoconjugate, erythromycin; and to a structurally-heterologous oligosaccharide derived from limited hydrolysis of gellan gum polysaccharide.