Abstract
A novel approach in glycosaminoglycomics, based on sheathless on‐line capillary electrophoresis/nanoelectrospray ionization‐quadrupole time of flight‐mass spectrometry (CE/nanoESI‐QTOF‐MS) and tandem MS of extended chondroitin sulfate/dermatan (CS/DS) oligosaccharide chains is described. The methodology required the construction of a new sheathless CE/nanoESI‐QTOF‐MS configuration, its implementation and optimization for the high sensitivity analysis of CS/DS oligosaccharide mixtures from conditioned culture medium of decorin transfected human embryonic kidney (HEK) 293 cells. Under newly established sheathless on‐line CE/(‐)nanoESI conditions for glycosaminoglycan (GAG) ionization and MS detection, single CS/DS oligosaccharide components of extended chain length and increased sulfation degree were identified. Molecular ions corresponding to species carrying 5 and 6 negative charges could be generated for large GAG oligosaccharide species in the negative ion nanoESI‐MS. The optimized on‐line conditions enabled the detection of molecular ions assigned to oversulfated tetradeca‐, octadeca‐, and eicosasaccharide CS/DS molecules, which represent the category of largest sulfated GAG‐derived oligosaccharides evidenced by CE/ESI‐MS. By on‐line CE/ESI tandem MS in data‐dependent acquisition mode the oversulfated eicosasaccharide species could be sequenced and the localization of the additional sulfate group along the chain could be determined.