Abstract
A new ionization method for the analysis of fragile gangliosides without undesired fragmentation or salt adduction is presented. In laserspray ionization inlet (LSII), the matrix/analyte sample is ablated at atmospheric pressure, and ionization takes place in the ion transfer capillary of the mass spectrometer inlet by a process that is independent of a laser wavelength or voltage. The softness of LSII allows the identification of gangliosides up to GQ1 with negligible sialic acid loss. This is of importance to the field of MS imaging, as undesired fragmentation has made it difficult to accurately map the spatial distribution of fragile ganglioside lipids in tissue. Proof-of-principle structural characterization of endogenous gangliosides using MS(n) fragmentation of multiply charged negative ions on a LTQ Velos and subsequent imaging of the GD1 ganglioside is demonstrated. This is the first report of multiply charged negative ions using inlet ionization. We find that GD1 is detected at higher levels in the mouse cortex and hippocampus compared with the thalamus. In LSII with the laser aligned in transmission geometry relative to the inlet, images were obtained in approximately 60 min using an inexpensive nitrogen laser.
Highlights
MATERIALS AND METHODSMatrixes 2,6-dihydroxyacetophenone (2,6-DHAP), 2,4,6-trihydroxyacetophenone (THAP), and 2,5-dihydroxybenzoic acid (2,5-DHB), and ganglioside standards from bovine brain GM1, GD1a, GD1b, and GT1b were purchased from Sigma Aldrich Inc
A new ionization method for the analysis of fragile gangliosides without undesired fragmentation or salt adduction is presented
Gangliosides are a class of glycosphingolipids (GSL) composed of an oligosaccharide chain anchored to a hydrophobic ceramide base
Summary
Matrixes 2,6-dihydroxyacetophenone (2,6-DHAP), 2,4,6-trihydroxyacetophenone (THAP), and 2,5-dihydroxybenzoic acid (2,5-DHB), and ganglioside standards from bovine brain GM1, GD1a, GD1b, and GT1b were purchased from Sigma Aldrich Inc. Ganglioside standards from bovine brain GD3 and GQ1b were purchased from Santa Cruz Biotechnology (Santa Cruz, CA). 2,5-dihydroxyacetophenone (2,5-DHAP) matrix and solvents acetonitrile, ethanol, and methanol were purchased from Fisher Scientific Inc. Matrixes and ganglioside standards were used without further purification
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