JMSSJ On-line

JMSSJ On-line, Vol. 55 (2007) No. 3, pp. 137-144

Study of Negative-Ion Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry of Neutral Oligosaccharides Ⅱ: Effcient Negative Ionization of Neutral Carbohydrates with Interaction between Matrix and Salt		>> Full Text PDF >> References
*Hiroaki SUZUKI^, Tohru YAMAGAKI, and Kazuo TACHIBANA** Department of Chemistry, School of Science, The University of Tokyo, TOKYO, JAPAN

Effcient ionization of neutral oligosaccharides in negative-ion matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was achieved; harmine (7-methoxy-1-methyl-9H-pyrido[3,4-b]indole) was used as a matrix and ammonium chloride was added as a chloride source to generate chlorinated molecules of neutral oligosaccharide. Increasing the molar amount of ammonium chloride gradually increased the ionization effciency, which was saturated by adding over 2 molar equivalents of ammonium chloride to the matrix. Ionization effciency increased when the concentration of salt was high. The results of solid phase fluorescence spectra of mixed crystals indicated that harmine was protonated and formed the hydrochloride salt. Results of ultraviolet absorption spectra showed that harmine hydrochloride absorbed ultraviolet laser irradiation from a nitrogen laser (337 nm) more effectively than harmine, and that ionization effciency of the chlorinated molecule increased. Harmine hydrochloride was the most effective matrix.

Key words: MALDI-MS, Effcient negative-ionization, Oligosaccharide