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Abstract:
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is a fast, reliable and sensitive technique for profiling of glycans and glycoconjugates and, therefore, widely used in glycobiology and glycobiotechnology. Although MALDI is considered to be a soft ionization technique the measurement of intact sialylated glycans or glycopeptides is a challenge due to in-source and metastable decay. The degree of desialylation is strongly influenced by the MALDI matrix applied. In this study we compared the established gold standard matrices 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA) with the recently introduced [1] new MALDI matrix 4-chloro-α-cyanocinnamic acid (Cl-CCA) for the measurement of sialylated N-glycopeptides as well as N- and O-glycans [2]. It was shown, that similar to the DHB matrix, the Cl-CCA matrix allowed the detection of sialylated N-glycans and N-glycopeptides in reflectron negative-ion mode MALDI-TOF-MS, which is not possible with the CHCA matrix. This finding could be attributed to reduced in-source decay for the “cold” matrices DHB and Cl-CCA as compared to the “hot” matrix CHCA. In contrast to DHB, Cl-CCA showed a microcrystalline nature with a homogeneous spatial distribution more similar to CHCA, which ensured a high shot-to-shot repeatability with improved mass accuracy and suitability for automated high-throughput measurements. Furthermore, Cl-CCA was in our hands superior to DHB and CHCA for detecting 1-phenyl-3-methyl-5-pyrazolone (PMP) labeled O-glycans in reflectron positive-ion mode MALDI-TOF-MS. In conclusion, the arsenal of suitable MALDI matrices for glycomics and glycoproteomics has been extended by this new rationally designed Cl-CCA matrix and its potential for glycosylation analysis has clearly been demonstrated. [1] Jaskolla, T.W.; Lehmann, W.D.; Karas, M. 4-Chloro-alpha-cyanocinnamic acid is an advanced, rationally designed MALDI matrix. Proc. Natl. Acad. Sci. U. S. A (2008), 105 (34), 12200-12205. [2] Selman, M.H.J.; Hoffmann, M.; Zauner, G.; McDonnell, L.A.; Balog, C.I.A.; Rapp, E.; Deelder, A.M.; Wuhrer, M.; MALDI-TOF-MS analysis of sialylated glycans and glycopeptides using 4-chloro-α-cyanocinnamic acid matrix. Proteomics (2012) accepted.
