engleski

Nano-electrospray ionization time-of-flight mass spectrometry of gangliosides from human brain tissues

A general approach for detection and structural elucidation of brain ganglioside species GM1, GD1 and GT1 by nano Electrospray-Ionization - Quadrupole-Time-of-Flight (nanoESI-QTOF) mass spectrometry, using combined data from MS and MS/MS analysis of isolated native ganglioside fractions in negative ion mode and their permethylated counterparts in positive ion mode is presented. This approach was designed to detect and sequence gangliosides, present in preparatively isolated ganglioside fractions from pathological brain samples available in only very limited amount. In these fractions mixtures of homologue and isobaric structures are present, depending on the ceramide composition and the position of the sialic acid attachment site. The interpretation of data for the entire sequence, derived from A, B, C and Y-ions in nanoESI-QTOF MS/MS negative ion mode of native fractions, can be compromised by ions arising from double and triple internal cleavages. To distinguish between isobaric carbohydrate structures in gangliosides, like monosialogangliosides GM1a and GM1b, disialogangliosides GD1a, GD1b and GD1c, or trisialogangliosides GT1b, GT1c and GT1d, the samples were analysed after permethylation in positive ion nanoESI-QTOF MS/MS mode, providing set of data, which allows clear distinction for assignment of outer and inner fragment ions according to their m/z values. The fragmentation patterns from native gangliosides obtained by low energy Collision Induced Dissociation (CID) by nanoESI-QTOF show common behavior and follow inherent rules. The combined set of data from negative and positive ion mode low energy CID can serve for detection of structural isomers in mixtures, and to trace new, not previously detected, components.

human brain gangliosides ; GM1 ; GD1 and GT1 ; nano-ESI-QTOF MS/MS ; low energy CID ; native and permethylated gangliosides

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