engleski

Glycomics of brain glycosaminoglycans by chip-based electrospray ionization ion trap multistage mass spectrometry

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in modulation of neuronal functions, brain development and some of its pathological states. To investigate the sulfation pattern of CS/DS structures expressed in CNS we developed a novel method based on an advanced system encompassing fully automated chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap (HCT) multistage mass spectrometry (MS2-MS3) by collision induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans, was particularly applied to structural investigation of disaccharides obtained by beta-elimination and digestion with chondroitin B and AC I lyase of hybrid CS/DS chains from a wild type mouse brain. Screening in the chip-MS mode of the DS disaccharide fraction, resulting after depolymerization with chondroitin B lyase, revealed molecular ions assigned to monosulfated disaccharide species having a composition of 4, 5-δ -[IdoA-GalNAc]. By optimized CID MS2-MS3, fragment ions supporting the localization of sulfate ester group at C-4 within GalNAc residue were produced. Chip ESI MS profiling of the CS disaccharide fraction, obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase, indicated the occurrence of mono- and bisulfated 4, 5-δ -[GlcA-GalNAc]. The site of oversulfation was determined by MS2-MS3, which provided sequence patterns consistent with a rare GlcA-3-sulfate-GalNAc-6-sulfate structural motif.

Glycosaminoglycans; mouse brain; multistage mass spectrometry

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