Matrix-assisted ultraviolet laser desorption/ionization time-of-flight mass spectrometry of beta-(1,3), beta (1,4)-xylans from Nothogenia fastigiata using nor-harmane as matrix

YUKO FUKUYAMA; ADRIANA A. KOLENDER; MASAE NISHIOKA; HIROSHI NONAMI; MARÍA C. MATULEWICZ; ROSA ERRA-BALSELLS; ALBERTO S. CEREZO

RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM.

John Wiley & Sons Ltd.

Lugar: Chichester, Gran Bretaña; Año: 2005 vol. 19 p. 349 - 358

0951-4198

Three xylan fractions, isolated from the red seaweed Nothogenia fastigiata (Nemaliales) were analyzed by ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOFMS). UV-MALDI-TOFMS was carried out in the linear and reflectron modes, and as routine in the positive- and negative-ion modes. Of the several matrices tested nor-harmane was the only effective one giving good spectra in the positive-ion mode. The number-average molar masses of two of the fractions, calculated from the distribution profiles, were lower than those determined previously by 1H NMR analysis, suggesting a decrease in the ionization efficiency with the molecular weight; weight-average molar mass and polydispersity index were also determined. As the xylans retained small but significant quantities of calcium salts, the influence of added Ca2+ as CaCl2 on UV-MALDI-MS was investigated. The simultaneous addition of sodium chloride and calcium chloride was also analyzed. Addition of sodium chloride did not change the distribution profile of the native sample showing that the inhibitory effect is due to Ca2+ and not to Cl-. Addition of calcium chloride with 1:1 analyte-salt molar ratio gave spectra with less efficient desorption/ionization of oligomers; the signals of these oligomers were completely suppressed when the addition of the salt became massive (1:100 analyte-salt molar ratio).