Negative ion fast atom bombardment mass spectrometry for native gangliosides using a neutral matrix

Sphingolipidomics: methods for the comprehensive analysis of sphingolipids

Sphingolipids comprise a highly diverse and complex class of molecules that serve as both structural components of cellular membranes and signaling molecules capable of eliciting apoptosis, differentiation, chemotaxis, and other responses in mammalian cells. Comprehensive or "sphingolipidomic" analyses (structure specific, quantitative analyses of all sphingolipids, or at least all members of a critical subset) are required in order to elucidate the role(s) of sphingolipids in a given biological context because so many of the sphingolipids in a biological system are inter-converted structurally and metabolically. Despite the experimental challenges posed by the diversity of sphingolipid-regulated cellular responses, the detection and quantitation of multiple sphingolipids in a single sample has been made possible by combining classical analytical separation techniques such as high-performance liquid chromatography (HPLC) with state-of-the-art tandem mass spectrometry (MS/MS) techniques. As part of the Lipid MAPS consortium an internal standard cocktail was developed that comprises the signaling metabolites (i.e. sphingoid bases, sphingoid base-1-phosphates, ceramides, and ceramide-1-phosphates) as well as more complex species such as mono- and di-hexosylceramides and sphingomyelin. Additionally, the number of species that can be analyzed is growing rapidly with the addition of fatty acyl Co-As, sulfatides, and other complex sphingolipids as more internal standards are becoming available. The resulting LC-MS/MS analyses are one of the most analytically rigorous technologies that can provide the necessary sensitivity, structural specificity, and quantitative precision with high-throughput for "sphingolipidomic" analyses in small sample quantities. This review summarizes historical and state-of-the-art analytical techniques used for the identification, structure determination, and quantitation of sphingolipids from free sphingoid bases through more complex sphingolipids such as sphingomyelins, lactosylceramides, and sulfatides including those intermediates currently considered sphingolipid "second messengers". Also discussed are some emerging techniques and other issues remaining to be resolved for the analysis of the full sphingolipidome.

High-resolution thin-layer chromatography of gangliosides

In this review an updated overview of current improvements on thin-layer chromatography (TLC) of gangliosides over the past decade is provided. Basic general techniques and special advice is given for successful separation of glycosphingolipids. New approaches concerning continuous and multiple development, and several preparative TLC methods are also included. Emphasis is placed on TLC immunostaining and related techniques, i.e. practical applications of carbohydrate-specific antibodies, toxins and bacteria, viruses, lectins and eukaryotic cells. Thus, this review on ganglioside TLC summarizes its power as an analytical tool for a wide range of purposes.

Preparation and characterization of four new variously deacetylated lysogangliosides, breakdown products of GM1

Four new deacylated lysogangliosides were obtained through alkaline hydrolysis of either C18 or C20 sphingosine homologues of GM1. By this procedure, both the fatty acids residue and the N-acetyl group of sialic acid were removed to give mono-N-acetyl-lysoGM1 (C18 and C20); the additional loss of the N-acetyl group of the acetylgalactosamine moiety gave de-N-acetyl-lysoGM1 (C18 and C20) with three free amino groups. The structures of four deacetylated lysogangliosides were unambiguously characterized by chemical analysis and 1H and 13C NMR spectroscopy as well as by negative ion FABMS. The aim of this study was to isolate pure breakdown products of gangliosides, enabling the evaluation of the mechanism of action of glycosphingolipids through their cleavage and identification of structures of potential pharmacological activity. These new substances were prepared as candidates to influence eicosanoid production and the mechanisms dependent on protein kinase C and phospholipase A2.

GM1b and GM1b-GalNAc: major gangliosides of murine-derived macrophage-like WEHI-3 cells

WEHI-3 cells, derived from a BALB/c mouse, are a myelomonocytic leukemic cell line with macrophage-like properties. We have isolated, purified and characterized the monosialogangliosides from WEHI-3 cells by 1D-HPTLC, 2D-HPTLC, enzymatic degradation, HPTLC-immunostaining, gas-liquid chromatography and fast atom bombardment-mass spectrometry (FAB-MS). Quantitative 2D-HPTLC shows two monosialogangliosides are the major components, constituting 77% of the total, with a third monosialoganglioside being 3%. The two major components were identified as (NeuAc)GM1b and (NeuAc)GM1b-GalNAc and the minor component as (NeuAc)GM1b-GalNAc-Gal. The presence of GM1b in this myelomonocytic cell line is consistent with its presence in other murine immune cells and tissues. GM1b-GalNAc and GM1b-GalNAc-Gal have been reported in T-lineage cells but not in resident or stimulated murine macrophages. Each of these monosialogangliosides belongs to the asialoGM1 synthetic pathway. Preliminary results indicate a disialo member of this pathway, GDlc, may also be present as a minor component. This ganglioside pathway, containing species which are not sialylated on the internal galactose, appears to be dominant in and may be characteristic of murine immune cells.

Characterization of glycosphingolipids by supercritical fluid chromatography-mass spectrometry

Gangliosides have been characterized by supercritical fluid chromatography-chemical ionization mass spectrometry (SFC-CIMS) as permethyl and pertrimethylsilyl derivatives, using carbon dioxide as the SFC mobile phase and CI reagent gas. Ganglioside classes and ceramide heterogeneity within each class are well resolved by SFC. Direct SFC-interfacing allows the analytical manipulations of single-ion monitoring, total-ion plots, background subtraction, library searches, and spectral reconstruction algorithms. Addition of ammonia to the CI ion chamber (NH3 as a CI reagent gas) yields abundant molecular-weight-related ions, (MH)+ and (MNH4)+ from analyte derivatives. Substitution of methanol for ammonia yields considerable parent-ion fragmentation, providing structural information on carbohydrate sequence, fatty acid, and sphingoid components. Under these latter conditions a unique alpha-cleavage fragment is observed which differentiates fatty acid from sphingosine heterogeneity. For ganglioside samples, the carboxyl group of neuraminyl residue(s) have been esterified with pentafluorobenzyl bromide and the products analyzed by negative ion chemical ionization MS. This modification improves chemical selectivity and greatly enhances detecting sensitivity. These "soft" ionization conditions provide abundant molecular-weight-related anions for collision-induced dissociation and subpicogram detection.

A sensitive assay of lysogangliosides using high-performance liquid chromatography

Lysogangliosides, LGM1, LGM2 and LGM3, each carrying a single sphingoid base (i.e., C18:1, C18:0, C20:1, C20:0), were prepared and a sensitive assay method of these lipids using HPLC was developed. The method involves fluorescence derivatization of the free amino group of the molecule with o-phthalaldehyde, separation of the molecular species of each lysoganglioside using reversed-phase HPLC and assay on the basis of a known amount of one of the lysogangliosides, as the internal standard. Using this method, lysoganglioside can be accurately assayed in the range of 5-1000 pmol. For assay of the lipid in the tissue, crude isolation procedures including extraction of lipids, Folch's partition and DEAE-Sepharose and AG 1-X2 column chromatographies were required before the fluorescence derivatization. In the normal human and the bovine cerebral cortex, 0.4-2.0 pmol/mg protein of LGM1 containing C18:1 and C20:1 sphingosine residues were detected. In the frontal cortex from a patient with Sandhoff disease, an abnormal accumulation (55-78 pmol/mg protein) of LGM2 was noted. Among various molecular species, LGM2 containing C18:1 was the most abundant.

Lysosulfatide (sulfogalactosylsphingosine) accumulation in tissues from patients with metachromatic leukodystrophy

We describe here a sensitive assay method for lysosulfatide (sulfogalactosylsphingosine) in human tissues using HPLC. The method involves extraction of lipids, saponification, isolation using a C18 Sep-Pak column, derivatization with o-phthalaldehyde, and detection of the fluorescent lysosulfatide using HPLC. In control subjects, a small amount of lysosulfatide was detected in the cerebral white matter (9-35 pmol/mg of protein), spinal cord (35 pmol/mg of protein), sciatic nerve (14 pmol/mg of protein), and kidney (approximately 2 pmol/mg of protein) but not in the cerebral gray matter and liver. A marked accumulation of the lipid was noted in tissues from six patients with metachromatic leukodystrophy (MLD). The concentration of lysosulfatide was high in the cerebral white matter, spinal cord, and sciatic nerve (223-1,172 pmol/mg of protein). Even in the cerebral gray matter, kidney, and liver, where lysosulfatide was hardly detected in the control sample, a considerable amount (3-45 pmol/mg of protein) accumulated in MLD patients. The concentration and distribution pattern of lysosulfatide were similar to those of galactosylsphingosine (psychosine) accumulated in patients with Krabbe disease. Therefore, the accumulation of lysosulfatide may explain the demyelination in patients with MLD, as is the case with Krabbe disease.