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A novel method for structural analysis of gangliosides based on nanoelectrospray multiple stage sequencing mass spectrometry

Development of modern mass spectrometry (MS) enabling multiple-stage fragmentation analysis of selected ions has considerably enhanced efficiency of biomolecule structural elucidation and applicability of MS in biochemistry/biomedicine. The last generation of MS instrumentation equipped with nanoelectrospray ionization (nanoESI) source and high-capacity ion storage trap (HCT) analyzer is particularly capable of providing an exhaustive structural identification. Gangliosides, a large group of sialylated glycosphingolipids, are primarily plasma-membrane components involved in cell-to-cell communication and cell signaling. Both abundance and structural diversity of ganglioside species is the highest in the brain of mammals. They are considered as biomarkers of human brain development, aging, and certain diseases, and their diagnostic/therapeutic potential is in the current focus of research. Our recent MS studies demonstrated that brain region-specific ganglioside patterns contain much larger number of individual species than previously reported. Detailed structural identification of individual species, specially distinguishing of various isomers, requires even more selective and thorough structural analysis. Our aim was to develop a novel protocol for systematic and thorough structural investigation of brain gangliosides based on negative ion mode nanoESI-HCT multiple stage MS fragmentation. The here-described approach was optimized to provide determination of ganglioside structural diversity including isomers. Concentration of the sample and instrumental parameters were reconsidered according to the particular requirements of the nanoESI multiple stage MS processes. Under optimized conditions, a complete set of structural data upon single species in a native human hippocampus ganglioside mixture of high complexity was obtained with excellent reproducibility of the experiments and a sample consumption situating the analysis sensitivity in the low picomolar range. Moreover, all MS stages, from MS1 screening to the MS4 stage of fragmentation, were obtained in one and same experiment, which required only five minutes of signal acquisition. The unique feature of the methodology to provide efficient multiple stage dissociation, ultra-high reproducibility, sensitivity, throughput and accurate structural data, offered a reliable characterization of hippocampus-associated ganglioside structure and a clear evidence upon the presence of certain positional isomers.

gangliosides; structural analysis; multiple stage sequencing mass spectrometry

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