Rapid and sensitive LC-ESI-MS of gangliosides.

Gangliosides are a class of sphingolipids characterized by a ceramide lipid chain attached to an anionic oligosaccharide moiety that varies in complexity based on the level of sialylation. Heterogeneity in the oligosaccharide chain of gangliosides is a direct result of the monosaccharide structure, content, sequence, and connections. Gangliosides are highly concentrated in the central nervous system, and are cell type-specific as well as development-dependent and their quantities and species can undergo drastic changes during cell differentiation. Specific localization of gangliosides also allows for interaction with a variety of bioeffectors, including glycoproteins, antibodies, peptide hormones, and growth factors. There are currently no rapid analytical assays capable of identifying and quantifying gangliosides. The aim of this study is to establish a reliable chromatographic mass spectrometry based assay capable of profiling ganglioside levels in complex biological samples at high sensitivity. We describe here a chromatographic method using an amino column on which the separation is based on hydrophilic interaction with the sugar moiety of gangliosides. Several gangliosides, including GM1-3, GD1a,b, GD2-3, and GT1a,b, were efficiently separated in less than 10 min at a limit of detection ranging between 10-50 pg on column with a concentration dynamic range extending over 4 orders of magnitude. The developed method allowed the sensitive quantitation of gangliosides derived from the blood serum of patients with different esophagus diseases, including, adenocarcinoma, high-grade dysplasia, and Barrett's.

Sugar nucleotide quantification using multiple reaction monitoring liquid chromatography/tandem mass spectrometry.

RATIONALE: Glycosylation of proteins and lipids is reliant on the availability of monosaccharide-activated donors known as sugar nucleotides. They are responsible for glycosylation in cells. Reliable quantification of these sugar nucleotides might provide an insight into their biological roles and attributes. METHODS: Herein, a method is described for the quantification of sugar nucleotides using ultra high pressure liquid chromatography (UHPLC) tandem mass spectrometry, allowing selective detection of sugar nucleotides in a biological sample. Seven model sugar nucleotide standards commonly associated with lipid and protein glycosylation were separated on a porous graphitic carbon column using an UHPLC system coupled to a triple stage quadrupole mass spectrometer utilizing a multiple reaction monitoring approach. RESULTS: Successful baseline separation of these metabolites was attained in 6 min using an ammonium formate buffer and acetonitrile, circumventing the use of MS-unfriendly pairing reagents. The linear dynamic range of this procedure was established over almost three orders of magnitude from 20 pg to 1 ng (40 pg to 2 ng for the isomers UDP-GlcNAc/GalNAc). The limit of detection ranged from 15 pg to 30 pg while the limit of quantification ranged from 50 pg to 100 pg. Furthermore, viability of this method was tested using three different breast cancer cell lines (MDA-MB-231, MDA-MB-231-BR, and MDA-MB-361) with the successful identification and quantification of all seven targeted sugar nucleotides. CONCLUSIONS: The described method permitted the quantitative analysis of sugar nucleotides in 10 min, thus allowing the practical use of this approach in high-throughput settings. The method was also very effective for the quantification of sugar nucleotides derived from three different breast cancer cell lines. The distribution of sugar nucleotides was different among the different cell lines and unique for each cell line.