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PubMed1988

Identification of partially methylated methyl glycosides by gas chromatography-mass spectrometry of trimethylsilyl derivatives. Application to mycobacterial glycolipid antigen analysis.

Partially methylated glycosides play an important role in the stereospecificity of glycolipid antigen-antibody binding reactions. A method for the structural determination of partially methylated methyl glycosides is described. The proposed method, which is an alternative to that using alditol acetates, consists in the analysis of trimethylsilyl glycoside derivatives by gas chromatography-mass spectrometry in the electron impact (EI) mode. Seven partially methylated methyl rhamnopyranosides were synthesized, then purified by high-performance liquid chromatography. After trimethylsilylation, their EI mass spectra showed characteristic fragmentation patterns allowing the determination of the position and the number of methoxy groups in the sugar ring. This method was successfully applied to the structural elucidation of partially methylated sugars contained by a quantitatively minor phenolic glycolipid antigen isolated from Mycobacterium kansasii. Moreover, the carbons involved in the glycosidic linkages of the glycolipid tetrasaccharide moiety were also identified by this method after permethylation, methanolysis and trimethylsilylation.

Antigens, Bacterial↗
PubMed2006

Activation of natural killer T cells by glycolipids.

Natural killer T (NKT) cells are a distinct T-cell sublineage, originally named because of their coexpression of an alphabeta T cell antigen receptor (TCR) characteristic of T lymphocytes, and NK1.1, a C-type lectin expressed by natural killer (NK) cells. NKT cells use their TCR to recognize glycolipids bound to or presented by CD1d. Until recently, most studies used the synthetic glycolipid alpha-galactosylceramide (alphaGalCer) to activate these lymphocytes, and very little was known about the natural antigens recognized by NKT cells. Given the pivotal role played by the NKT cells in many immune responses, including antimicrobial responses, tumor rejection, and the development of autoimmune diseases, the identification of the natural antigens recognized by these cells, and analogs that may alter their cytokine production, are goals of primary importance. This chapter discusses methods that can be used to assess the potency of potential glycolipid antigens for this unique population of T lymphocytes, including methods for in vitro NKT cell activation and expansion, in vivo activation, and measurement of their avidity for different antigens.

Animals↗
PubMed2000

Role of the cell wall phenolic glycolipid-1 in the peripheral nerve predilection of Mycobacterium leprae.

The cell wall of pathogenic mycobacteria is abundant with complex glycolipids whose roles in disease pathogenesis are mostly unknown. Here, we provide evidence for the involvement of the specific trisaccharide unit of the phenolic glycolipid-1 (PGL-1) of Mycobacterium leprae in determining the bacterial predilection to the peripheral nerve. PGL-1 binds specifically to the native laminin-2 in the basal lamina of Schwann cell-axon units. This binding is mediated by the alpha(2LG1, alpha2LG4, and alpha2LG5 modules present in the naturally cleaved fragments of the peripheral nerve laminin alpha2 chain, and is inhibited by the synthetic terminal trisaccharide of PGL-1. PGL-1 is involved in the M. leprae invasion of Schwann cells through the basal lamina in a laminin-2-dependent pathway. The results indicate a novel role of a bacterial glycolipid in determining the nerve predilection of a human pathogen.

Animals↗
PubMed1993

Steric presentation and recognition of the saccharide chains of glycolipids at the cell surface: favoured conformations of the saccharide-lipid linkage calculated using molecular mechanics (MM3).

The orientation of the saccharide moiety of glycolipids at the membrane surface is determined by an interplay of different steric factors, e.g. the conformation of the saccharide chain, the conformation of the saccharide-lipid linkage and restrictions due to the membrane surface. In the present study the preferred conformations of the saccharide-lipid linkages of glucosylceramides with normal and hydroxy fatty acids and glucosyldiglycerides with acyl and alkyl chains were studied using molecular mechanics (MM3). The populations of different conformers were calculated on the basis of relaxed energy maps. Calculations on glucosylceramides at a dielectric constant (epsilon) of 4 showed three dominating conformers: phi/psi/theta 1 = +sc/ap/-sc (global energy minimum), /-sc/ap and +sc/ap/ap, respectively. In sphingolipids the +sc rotamer of theta 1 is disfavoured due to a Hassel-Ottar interaction involving the sphingosine O1 and O3 oxygen atoms. alpha-O Hydroxylation of the fatty acid does not significantly affect the conformational preferences of the saccharide-ceramide linkage at epsilon-values relevant for biomembranes. In glycoglycerolipids the global energy minimum is shifted to the phi/psi/theta 1 = +sc/ap/ap conformation. For glycolipids located in membranes additional steric restrictions are imposed by the surrounding lipid layer. These restrictions in the steric presentation appear to be of crucial significance for the selective recognition and crypticity of glycolipids in membranes.

Carbohydrate Conformation↗
PubMed2002

Structure of the major glycolipid from Rothia dentocariosa.

Structural studies of the major glycolipid isolated from Rothia dentocariosa were carried out by specific chemical degradation and nuclear magnetic resonance spectroscopy. The glycolipid was found to be a dimannosylacylmonoglyceride in which the carbohydrate part was the glycerol-linked dimannoside alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-sn-Gro, and the internal mannose was esterified at C-6 by fatty acid residue. The other fatty acyl chain substituted the primary methylene position of glycerol. The occurrence of this glycolipid is limited to the related microorganisms. The structural characteristics can facilitate the differentiation of some genera.

Acetone↗
PubMed1998

Serotaxonomic analysis of glycolipids from Mycobacterium chelonae-M. fortuitum complex and bovine farcy strains.

The antigenicity and cross-reactivity of glycolipids from strains of bovine farcy and the Mycobacterium chelonae-M. fortuitum complex were analyzed using the ELISA technique. Purified alkali-stable glycopeptidolipids (GPLs) with a characteristic dimethylrhamnosyl sugar unit extracted from M. abscessus, M. chelonae, M. peregrinum and M. senegalense, gave very strong reactions with sera against members of the same four species. Particularly strong cross-reactions were evident between M. peregrinum and M. senegalense. These GPLs reacted more weakly with antisera against the other mycobacteria tested, though clear reactions were noticed with M. farcinogenes and M. fortuitum and also with M. bovis BCG, M. phlei, and M. tuberculosis strains. Alkali-labile diacyl trehalose (DAT) and triacyl trehalose (TAT) from M. fortuitum reacted with homologous sera, and with that against M. tuberculosis. Traces of uncharacterized acyl trehaloses isolated from two strains of M. farcinogenes gave comparatively weak reactions. Mycobacteria labeled M. farcinogenes and M. senegalense produced glucosylated trehalose-based glycolipids (GTs) and the studies showed that the major type was antigenic. These glycolipids cross-reacted strongly with M. senegalense NCTC 4524 but not with the type strain of M. senegalense. On the basis of the chemical patterns and the antigenicity of the GPLs it is evident that M. peregrinum and M. senegalense are particularly closely related and these species show a very close affinity to M. abscessus-M. chelonae.

Animals↗
PubMed1999

Isolation and characterization of novel neutral glycolipids from Thermoplasma acidophilum.

Several novel neutral glycolipids (GL-1a, GL-1b, GL-2a, GL-2b and GL-2c) were isolated from Thermoplasma acidophilum by high-performance liquid chromatography using phenylboronic acid-silica and preparative thin-layer chromatography. The tentative structures of these lipids were characterized by the combination of gas-liquid chromatography, the methylation procedure, and (1)H-NMR and FAB-mass spectrometries. The lipophilic portion of the neutral glycolipids was composed of a simple molecular species named caldarchaeol (dibiphytanyl-diglycerol tetraether). The sugar moieties of these glycolipids were composed of gulose and glucose which formed monosaccharide residues on one side or both sides of the core lipids. Gulose was attached to the terminal glycerol OH group of the core lipid with a beta-configuration and glucose being attached with an alpha-configuration. The proposed structure of GL-1a was gulosylcaldarchaeol and that of GL-1b was glucosylcaldarchaeol. The structures of GL-2a, GL-2b, and GL-2c were the analogs of the caldarchaeol derivatives attached by a variety of gulosyl residues or glucosyl residues on both sides of the terminal OH groups.

Carbohydrates↗
PubMed1992

Structure of a novel sulfate-containing mycobacterial glycolipid.

We described previously the unusual structures of the two major C-mycoside glycopeptidolipids from Mycobacterium fortuitum biovar. peregrinum. More polar glycolipids, potentially more interesting in terms of antigenicity, were also present in the strains. A combination of FAB mass spectrometry, NMR, chemical analyses, and radiolabeling was successfully applied to these glycolipids to arrive at the unexpected and novel structure for the more polar compound. This consisted of the "orthodox" basic structure of the apolar C-mycosides, modified at the alaninol end by the presence of a sulfate group on position 2 of a 3,4-di-O-methylrhamnosyl residue. This novel and second class of sulfate-containing mycobacterial glycolipid may provide a chemical basis for the differentiation and classification of members of the M. fortuitum complex, the main group causing human diseases among the many fast-growing mycobacteria widely distributed in nature.

Chromatography, Thin Layer↗
PubMed1988

Lipid composition of PC12 pheochromocytoma cells: characterization of globoside as a major neutral glycolipid.

We have studied the lipid composition of PC12 pheochromocytoma cells cultured in the presence and absence of nerve growth factor (NGF). Neutral and acidic lipid fractions were isolated by column chromatography on DEAE-Sephadex and analyzed by high-performance thin-layer chromatography (HPTLC). The total lipid concentration was approximately 220 micrograms/mg of protein, and the concentration of neutral glycolipids was 1.6-1.8 microgram/mg of protein for both NGF-treated and untreated cells. The neutral glycolipid fraction contained a major component, which accounted for approximately 80% of the total and which was characterized as globoside on the basis of HPTLC mobility, carbohydrate analysis, fast atom bombardment mass spectrometry, and mild acid hydrolysis. The major fatty acids of globoside were C16:0 (10%), C18:0 (16%), C22:0 (23%), C24:1 (17%), and C24:0 (24%). C18 sphingenine accounted for almost all of the long-chain bases. The other neutral glycolipids were tentatively identified as glucosylceramide (15%), lactosylceramide (4%), and globotriosylceramide (4.5%). The concentration of ganglioside sialic acid was approximately 0.34 and 0.18 microgram/mg of protein for cells grown in the presence and absence of NGF, respectively. Although there was an increase in ganglioside concentration in NGF-treated cells, NGF did not produce any differential effects on the relative proportions of the individual gangliosides. Several of the gangliosides appear to contain fucose, and one of these was tentatively identified as fucosyl-GM1. Brain-type gangliosides of the ganglio series were also detected by an HPTLC-immunostaining method. However, the fatty acid and long chain base compositions of PC12 cell gangliosides (and their TLC mobility) differ from those of brain gangliosides.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1988

Influence of head-group interactions on the miscibility of synthetic, stereochemically pure glycolipids and phospholipids.

Phase diagrams of binary mixtures of the glycoglycerolipids 1,2-di-O-tetradecyl-3-O-beta-D-galactosyl-sn-glycerol (14-Gal) and 1,2-di-O-tetradecyl-3-O-beta-D-glucosyl-sn-glycerol (14-Glc) with the phospholipids L-dimyristoylphosphatidylcholine (DMPC) and L-dimyristoylphosphatidylethanolamine (DMPE) were recorded by high-sensitivity differential scanning calorimetry and used for determination of the glycolipid-phospholipid miscibility in solid and liquid-crystalline states. As a consequence of a metastable behavior of both glycolipids and DMPE, the solid-state glycolipid/phospholipid miscibility was strongly dependent on the temperature prehistory of the samples. While DMPC and 14-Glc mix continuously, the other three binaries display extended regions of solid-solid-phase separation in the equilibrium low-temperature states. The DMPE/glycolipid phase diagrams were of clearly expressed eutectic type. Continuous solutions were formed in the liquid-crystalline and in the metastable solid phases of the mixtures. Simulations of the shape of the phase diagrams using the Bragg-Williams approximation showed certain deviations from ideal mixing in the liquid-crystalline continuous solutions. Since both glycolipids and phospholipids contain fully saturated fatty acids of equal chain length, their mixing properties were predominantly determined by the interactions between the lipid polar moieties, assuming the influence of ester or either linkages of the alkyl chains on the mixing parameters to be negligible. The clearly expressed differences in the mixing of 14-Glc and 14-Gal with phospholipids are most probably due to different hydrogen-bond networks formed by the glucosyl and galactosyl residues.

Calorimetry, Differential Scanning↗
PubMed1980

Lectin-mediated aggregation of liposomes containing glycolipids with variable hydrophilic spacer arms.

Synthetic glycolipids containing a cholesterol anchor group attached via a spacer group to a sugar moiety can be incorporated into small unilamellar liposomes, rendering them susceptible to agglutination by the appropriate multivalent lectin [Rando, R. R., Orr, G. A., & Bangerter, F. W. (1979) J. Biol. Chem. 254, 8318-8323; Rando, R. R., & Bangerter, F. W. (1979) J. Supramol. Struct. 11, 295-309]. We report here on the role of spacer arm length in rendering these liposomes susceptible to agglutination. In order to eliminate the ambiguities inherent in using hydrophobic or charged spacer groups, we have synthesized a hydrophilic, ethylene glycol based amino acid (8-amino-3,6-dioxaoctanoic acid) for these studies. The Ricinus communis agglutinin (ricin) mediated agglutination of these beta-galactoside-containing glycolipids was studied. A spacer arm length of four atoms will not support agglutination under any conditions. A seven-atom spacer will support agglutination, but only at high phospholipid concentrations (0.24 mumol/mL) with a pseudo-first-order rate of agglutination of 0.0079 min-1. With 13 and 22 atom spacer groups, the pseudo-first-order rate constants were 0.4 min-1 and 1.3 min-1, respectively, at a phospholipid concentration of 0.06 mumol/mL. Under conditions where the liposomes containing the glycolipid with the 13-atom hydrophilic spacer arm were completely agglutinated by ricin, 9.3% of the total available sugar moieties of the liposome were bound to ricin. This means that, on the average, 38 interliposomal bonds were formed in an aggregate.

Agglutination↗
PubMed1976

Lipoteichoic acid from Bacillus licheniformis 6346 MH-1. Comparative studies on the lipid portion of the lipoteichoic acid and the membrane glycolipid.

A lipoteichoic acid and a membrane glycolipid were isolated from Bacillus licheniformis 6346 MH-1. The fatty acid composition of the two preparations were similar. Most of the fatty acids were of the branched chain type. The glycolipid was shown to be a diacyl derivative of O-beta-D-glucopyranosyl-(1 leads to 6)-O-beta-D-glucopyranosyl-(1 leads to 3)-glycerol. The lipoteichoic acid contained lipid, polyglycerol phosphate, and glucosamine. The lipid was released by treatment with hydrofluoric acid and by hydrolysis in dilute acid and was shown to have a structure identical with that of the membrane glycolipid.

Bacillus↗
PubMed2000

A novel glycolipid and phospholipid in the purple membrane.

A novel glycolipid of mass 1935 and a phospholipid of mass 1522 are the main residual lipids (along with traces of PGP-Me, S-TGD-1, and PG) specifically associated with "delipidated" bacteriorhodopsin fractions BR I and BR II, prepared by Triton X-100 treatment of purple membrane (PM), from a genetically engineered strain (L33) of Halobacterium salinarum, and chromatography on phenyl-Sepharose CL-4B. The novel glycolipid and phospholipid are components of the PM matrix not previously described. The TLC isolated and purified novel glycolipid and phospholipid were shown, by chemical degradation, mass spectrometry, and NMR analyses, to have the structure, respectively, of a phosphosulfoglycolipid, 3-HSO(3)-Galp-beta1,6Manp-alpha1,2Glcp-alpha1,1-[sn-2, 3-di-O-phytanylglycerol]-6-[phospho-sn-2,3-di-O-phytanylglycero l], and of a glycerol diether analogue of bisphosphatidylglycerol (cardiolipin), sn-2,3-di-O-phytanyl-1-phosphoglycerol-3-phospho-sn-2, 3-di-O-phytanylglycerol.

Bacteriorhodopsins↗
PubMed2004

Spacer-arm modulated gene delivery efficacy of novel cationic glycolipids: design, synthesis, and in vitro transfection biology.

Design, syntheses and relative in vitro gene delivery efficacies of six novel cationic glycolipids 1-6 containing open-form galactosyl units in CHO, COS-1, MCF-7 and A549 cells are described. The results of the present structure-activity investigation convincingly demonstrate that the in vitro gene delivery efficacies of galactosylated cationic glycolipids are strikingly dependent on the absence of a spacer-arm between the open-form galactose and the positively charged nitrogen atom in their headgroup region. While the cationic glycolipids 1-3 with no headgroup spacer unit between the positively charged nitrogen and galactose showed high in vitro gene transfer efficacies in all four cells (lipids 1 and 2 with myristyl and palmityl tails, respectively, being the most efficacious), lipids 4-6 with five-carbon spacer units between the quaternized nitrogen and galactose heads were essentially transfection incompetent. The transfection inhibiting role of the five-carbon spacer unit in the headgroup region of the present novel class of cationic lipids was demonstrated by both beta-galactosidase reporter gene expression and histochemical X-gal staining assays. Results of MTT assay-based cell viability measurements in representative MCF7 cells show that cell viabilities of lipoplexes (lipid:DNA complexes) prepared from all the lipids 1-6 are remarkably high. Thus, possibilities of differential cellular cytotoxicities playing any key role behind the strikingly contrasting transfection properties of lipids 1-3 with no spacer and lipids 4-6 with a spacer unit in the headgroup regions was ruled out. Electrophoresis gel patterns in DNase I sensitivity assays are consistent with more free DNA (accessible to DNase I) being present in lipoplexes of lipids 4-6 than in lipoplexes of lipids 1-3. Thus, the results of our DNase I protection experiments support the notion that enhanced degradation of DNA associated with lipoplexes of lipids 4-6 may play an important role in abolishing their in vitro gene transfer efficacies.

Animals↗
PubMed1997

New acylated sulfoglycolipids and digalactolipids and related known glycolipids from cyanobacteria with a potential to inhibit the reverse transcriptase of HIV-1.

Five novel diacylated sulfoglycolipids (1-5) were isolated from the cyanobacterium Scytonema sp. (TAU strain SL-30-1-4) and four novel acylated diglycolipids (6-9) were isolated from the cyanobacterium Oscillatoria raoi (TAU strain IL-76-1-2). These two groups of glycolipids and related known glycolipids isolated from these two and three other strains of cyanobacteria, Phormidium tenue (TAU strain IL-144-1), O. trichoides (TAU strain IL-104-3-2), and O. limnetica (TAU strain NG-4-1-2), were found to inhibit HIV-1 RT enzymatic activity to different extents. The structure elucidation of the various compounds is based on the selective hydrolysis of the glycerol ester moieties, GCMS analysis of the methyl ester derivatives of the liberated fatty acids, homo- and heteronuclear-2D-NMR techniques, and MS. The use of negative-ion FABMS for analyzing the combination and distribution of the fatty acids in glycolipids is demonstrated.

Cyanobacteria↗
PubMed1999

Involvement of glycolipid-enriched domains in the transduction mechanism of neurotrophins in cultured neurons.

Specialized domains, displaying a peculiar lipid and protein composition, are present within the plasma membrane of mammalian cells and play a pivotal role in fundamental membrane-associated events. Among lipids, sphingolipids (in particular glycolipids and sphingomyelin) are characteristically enriched within such domains. Moreover, a series of functionally related proteins is present, suggesting the involvement of these membrane structures in the mechanism of signal transduction and lipid/protein sorting. An increasing body of evidence suggests that domains are dynamic structures, and that their dynamic fluctuations can modulate the activity of domain-associated proteins through changes of glycolipid protein interaction. Even if a large body of experimental investigation has been carried out on eukaryotic cells, only little attention has been paid to the neuron. The purpose of the present review is to summarize the observations implying a functional role of glycolipid-enriched domains in cultured rat cerebellar granule cells.

Animals↗
PubMed1993

Sulfolipids and glycolipid sulfotransferase activities in human renal cell carcinoma cells.

A cell line (SMKT-R3) established from human renal cell carcinoma was characterized for the presence of sulfolipids and glycolipid sulfotransferases. Sulfolipids were found to constitute a large part of the acidic glycolipid fraction in SMKT-R3 cells. These findings were confirmed by metabolic labelling with 35S-sulfate. These sulfolipids were expressed at the surface of SMKT-R3 cells as ascertained by cytofluorometry using a monoclonal antibody directed to sulfolipids. Furthermore, markedly high activity levels of glycolipid sulfotransferases were observed in SMKT-R3 cells compared with other cell lines. These results suggest that the increased synthesis of sulfolipids in renal cell carcinoma tissue (Sakakibara et al., 1989. Cancer Res., 49, 335-339) is due to the elevation of the sulfotransferase activities of renal carcinoma cells themselves.

Carcinoma, Renal Cell↗
PubMed1978

Hepatic storage of oligosaccharides and glycolipids in a cat affected with GM1 gangliosidosis.

1. Glycopeptides and glycolipids were isolated from normal cat liver and liver from a cat affected with GM1 gangliosidosis. 2. Bio-Gel P-6 chromatography of the crude glycopeptide fractions demonstrated three major peaks of hexose-containing compounds that were greatly increased in the mutant liver sample; these peaks contained oligosaccharides that comprised over 2% of the liver wet weight. 3. Two of the major pathological oligosaccharides, GP5 and GP6, were purified by chromatography on charcoal/Celite and Sephadex G-25. Oligosaccharides GP5 and GP6 had apparent mol.wts. of 1800 +/- 200 and 1350+/-200 respectively, and contained galactose, mannose and N-acetylglucosamine in molar proportions of 2.0:3.1:4.1 (GP5) and 1.0:2.2:2.7 (GP6). Periodate oxidation studies demonstrated the presence of galactose in a non-reducing terminal position. 4. The neutral glycolipid fraction from the mutant cat liver has a 1.3-fold increase in hexose content accompanied by an increased concentration of asialo-(ganglioside GM1). 5. There was a 2-fold increase of gangliosides in the mutant cat liver compared with normal cats. Ganglioside GM1 and a compound tentatively identified as N-glycolloyl-(ganglioside GM1) were the major glycolipids accumulated.

Animals↗