Sensitive analyses of neutral N-glycans using anion-doped liquid matrix G3CA by negative-ion matrix-assisted laser desorption/ionization mass spectrometry.
Negative-ion fragmentation of N-glycans has been proven to be more informative than that of positive-ion. In particular, it defines structural features such as the specific composition of the two antennae and the location of fucose. However, negative-ion formation of neutral N-glycans by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) remains a challenging task, and the detection limit of N-glycans in negative-ion mode is merely at the subpicomole level. Thus, practical applications are limited. In this study, combinations of five liquid matrices and nine anions were used to ionize N-glycans as anionic adducts, and their performances for sensitive analyses were evaluated. The best results were obtained with anion-doped liquid matrix G(3)CA, which consists of p-coumaric acid and 1,1,3,3-tetramethylguanidine; the detection limits of anion adducted N-glycans were 1 fmol/well for NO(3)(-), and 100 amol/well for BF(4)(-). Negative-ion MS(2) spectra of 1 fmol N-glycans were successfully acquired with a sufficient signal-to-noise ratio and were quite useful for MS-based structural determination. The anion-doped G(3)CA matrix opens the way for sensitive and rapid analysis of neutral N-glycans in negative-ion MALDI at a low femtomole level.
Koichi Tanaka Laboratory of Advanced Science and Technology, Shimadzu Corporation, Nakagyo-ku, Kyoto, Japan. nishikaz@shimadzu.co.jp
Takashi
T
Nishikaze
Yuko
Y
Fukuyama
Shin-ichirou
S
Kawabata
Koichi
K
Tanaka
D000838:Anions / Q000737:chemistry; D003373:Coumaric Acids / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D006146:Guanidines / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis* / Q000737:chemistry*; D011422:Propionates; D059629:Signal-To-Noise Ratio; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D000838:Anions; D003373:Coumaric Acids; D005740:Gases; D006146:Guanidines; D011134:Polysaccharides; D011422:Propionates; C495469:p-coumaric acid; C477069:1,1,3,3-tetramethylguanidine