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Y. Zhang, T. Iwamoto, G. Radke, Y. Kariya, K. Suzuki, A. H. Conrad, J. M. Tomich, G. W. Conrad; Identification of Corneal Keratan Sulfate by MALDI-TOF/TOF Mass Spectrometry. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1481.
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To identify bovine corneal keratan sulfate oligosaccharides using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) with optimized conditions.
Keratan sulfate mono-, di-, tri-, and tetra-sulfated oligosaccharides and sialylated KS oligosaccharides were derivatized with pyrenebutyric acid hydrazide (PBH). Identification of the derivatized KS oligosaccharides was achieved in combination with the optimal 2,5-dihydroxybenzoic acid (DHB) matrix using MALDI-TOF-MS and MALDI-TOF/TOF-MS under negative ionization mode.
This work demonstrates that PBH derivatization can greatly increase the detector response to KS oligosaccharides. The MALDI-TOF-MS spectra of mono-sulfated disaccharides exhibit molecular ion [M - H] -. However, multiply-sulfated KS oligosaccharides reveal a singly charged ion corresponding to the molecular ion [M + nNa - (n+1)H] -, where n = the number of sulfates. The MALDI-TOF/TOF-MS/MS spectra showed the fragmentation of glycosidic linkages with mainly Y/B/C ions, as well as various cross-ring cleavages (i.e., X/A ions), providing precise structural information for identifying important features of KS oligosaccharides. Thus, these diagnostic ions can be used to construct fingerprint maps to identify significant structural domains of unknown KS oligosaccharides without prior purification.
A simple, rapid, sensitive, novel method for MALDI-TOF/TOF mass spectrometric analysis of KS oligosaccharides is described.
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