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At least 811 records · Page 45Linked to original sources
PubMed1987

Fluorometric high-performance liquid chromatography of N-acetyl- and N-glycolylneuraminic acids and its application to their microdetermination in human and animal sera, glycoproteins, and glycolipids.

A simple, rapid, and highly sensitive high-performance liquid chromatographic method is described for the determination of N-acetyl- and N-glycolylneuraminic acids in human and animal sera, glycoproteins, and glycolipids. The neuraminic acids, released by acid hydrolysis of these biological samples, are converted in dilute sulfuric acid with 1,2-diamino-4,5-methylene-dioxybenzene, a fluorogenic reagent for alpha-keto acids, to highly fluorescent derivatives. The derivatives are separated within 12 min on a reversed-phase column (Radial-Pak cartridge C18) with an isocratic elution and detected fluorometrically. The detection limits are 25 fmol (7.7 pg) for N-acetylneuraminic acid and 23 fmol (7.5 pg) for N-glycolylneuraminic acid in a 10-microliter injection volume at a signal-to-noise ratio of 2. This method permits precise determination of the neuraminic acids in 5 microliter of human and animal sera or in 0.25-2.5 micrograms of glycoproteins and glycolipids.

Animals↗
PubMed1988

Sulfated glycolipids and cell adhesion.

The adhesive glycoproteins laminin, thrombospondin, and von Willebrand factor bind specifically and with high affinity to sulfatides, and it is this binding that probably accounts for their ability to agglutinate glutaraldehyde-fixed erythrocytes. The three proteins differ, however, in the inhibition of their binding to sulfatides by sulfated polysaccharides. Fucoidan strongly inhibits binding of both laminin and thrombospondin, but not of von Willebrand factor, suggesting the involvement of laminin or thrombospondin, or other unknown sulfatide-binding proteins in specific cell interactions that are also inhibited by fucoidan. Thrombospondin adsorbed on plastic promotes the attachment and spreading of some melanoma cells. Interestingly, fucoidan and an antibody against the sulfatide-binding domain of thrombospondin selectively inhibit spreading but not attachment to thrombospondin-coated surfaces. Sulfatides, but not neutral glycolipids or gangliosides, when adsorbed on plastic also promote attachment and spreading of some cultured cell lines. Direct adhesion of melanoma cells requires high densities of adsorbed sulfatide. In the presence of laminin, however, specific adhesion of some cell types to sulfatide is strongly stimulated and requires only low densities of adsorbed lipid, suggesting that laminin is mediating adhesion by crosslinking receptors on the cell surface to sulfatide adsorbed on the plastic. Although thrombospondin also binds to sulfatides and to melanoma cells, it does not enhance but rather inhibits direct and laminin-dependent melanoma cell adhesion to sulfatide, presumably because it is unable to bind simultaneously to ligands on opposing surfaces. Thus, sulfated glycolipids can participate in both laminin- and thrombospondin-mediated cell adhesion, but their mechanisms of interaction are different.

Animals↗
PubMed1991

Verotoxin-resistant cell clones are deficient in the glycolipid globotriosylceramide: differential basis of phenotype.

Escherichia coli-derived verotoxin is an extremely toxic protein and is highly selective toward certain primate cells. Two susceptible cell lines are the Daudi cell line (human Burkitt lymphoma) and the Vero cell line (Green African monkey kidney). Both of these cell lines contain significant levels of the verotoxin binding glycolipid globotriosylceramide (Gb3) (1 nmol/10(7) cells and 3 nmol/10(6) cells, respectively). A clone was selected from the Vero cell line for resistance to Verotoxin 2, while a mutant from the Daudi cell line was selected for resistance to Verotoxin 1. Both were found to be deficient in globotriosylceramide with a corresponding increase in the precursor glycolipid lactosylceramide. Cell free assay of alpha-galactosyltransferase activity revealed that the Vero cell clone (VRP) contained significantly reduced enzyme activity, whereas in the case of the Daudi mutant (VT20), no significant decrease in activity was noted in vitro. These observations suggest a complex regulation of Gb3 biosynthesis which is considered in relation to P blood group antigen expression.

Animals↗
PubMed1983

Glycolipid crypticity in membranes--not a simple shielding effect of macromolecules.

The potential of membrane-bound macromolecules for shielding glycolipids from involvement in specific binding events was considered in model membranes. Serum albumin and several Dextrans were covalently derivatized with oleic acid so that they adsorbed irreversibly to lipid bilayers. This provided a means of generating bilayer membranes with a considerable layer of attached material. Gangliosides dispersed in such membranes were subjected to attack by the enzyme, neuraminidase, in order to assess their "accessibility'. We were surprised to find that we could not demonstrate any significant reduction in ganglioside hydrolysis in phosphatidylcholine bilayers bearing extensive surface coats of protein or polysaccharide. We conclude that non-specific, physical shielding by macromolecules is an unlikely source of the often-observed "crypticity' of glycolipids at the cell surface. Consistent with this interpretation was a relative lack of headgroup motional restriction seen for spin-labelled ganglioside headgroups in the same bilayers and in cell membranes.

Electron Spin Resonance Spectroscopy↗
PubMed1985

Influence of glycolipids on immune reactions of phospholipid antigens in liposomes.

Complement-dependent immune damage to liposomes mediated by a murine monoclonal antibody to the liposomal bilayer was completely inhibited by ceramide tetrasaccharide (globoside) at an 8% concentration in the liposomes. Lower concentrations of globoside, or higher concentrations of ceramide tri-, di-, or monohexoside, were not inhibitory. At a globoside concentration of 5.8%, inhibition of the monoclonal antibody activity was reduced and inhibition was related to antibody concentration; but at 2% globoside, suppression of antibody activity was not observed at all. Analysis of space-filling models revealed that at 8% globoside the distance between adjacent tetrasaccharides of globoside approached the dimensions of the antigen-binding end of a 7S immunoglobulin molecule. We therefore propose that globoside, and perhaps other glycolipids, can exert steric hindrance to the binding of extracellular proteins to nonglycolipid constituents of the lipid bilayer. We conclude that microheterogeneity among polar groups of glycolipids may be a novel mechanism for allowing selective access of proteins to phospholipids on the lipid bilayer.

Animals↗
PubMed1988

Deuterium NMR studies of the interactions of polyhydroxyl compounds and of glycolipids with lipid model membranes.

The physical properties of bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the presence of four water-soluble polyhydroxyl compounds, trehalose, sorbitol, glycerol, and ethyleneglycol, and three neutral glycolipids - monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and nonhydroxy fattyacyl-cerebrosides (NHFA-Cer) - were investigated using 2H-NMR. All four polyhydroxyl compounds induced small, but comparable concentration-dependent changes in the choline headgroup conformation which were consistent with the presence of a small negative charge being conferred upon the bilayer surface. The latter may be explained by dipolar interactions brought about by changes in the long-range order of the water layer at the membrane surface. Trehalose had a small ordering effect on the hydrophobic interior of the membrane while ethyleneglycol induced a disordering, at both the head group level and in the hydrophobic interior. The presence of high amounts of carbohydrate at the membrane surface was ensured when POPC was mixed with various proportions of one of three glycolipids, MGDG, DGDG and NHFA-Cer. In these cases the conformation of the choline headgroup was only marginally altered when not masked by macroscopic phase changes. The headgroup conformational changes observed in the presence of any of the above-mentioned compounds were modest in comparison to the effects induced by charged substances.

Ethylene Glycol↗
PubMed1989

Dynamics and orientation of glycolipid headgroups by 2H-NMR: gentiobiose.

Deuterium nuclear magnetic resonance has been used to investigate the dynamics and determine the orientation of the headgroup of the glycolipid 1,2-di-O-tetradecyl-3-O-(6-O-beta-D-glucopyranosyl-beta-D-glucopyranosyl )-sn- glycerol (beta-DTDGL), in aqueous multilamellar dispersions. In addition, its anomeric analog, having an alpha glucose-glycerol linkage, was prepared and examined. The lipids were labelled with deuterium at specific positions in the disaccharide moiety. Analysis of the deuterium quadrupolar splittings for the first glucose ring (glycerol-linked) gave segmental order parameters of 0.43 and 0.35 for the beta and alpha isomers, respectively. Both isomers had similar orientations of the sugar ring relative to the bilayer surface, as determined for lipid in the liquid-crystalline phase. 2H-NMR results for the lipid labelled at C-6' are consistent with a single conformation about the C-5'-C-6' bond of the first glucose residue, with a dihedral angle (O-5'-C-5'-C-6'-O-6') of -17 degrees. The results obtained for the second sugar ring suggest that two conformers may be present, which are in slow exchange on the 2H-NMR timescale. Measurements of longitudinal relaxation times, T1z, gave similar values for both sugar moieties in the headgroup, suggesting that the disaccharide does not exhibit the flexibility expected about the 1----6 linkage. Since T1z for 2H in these compounds decreases with increasing temperature and increases with magnetic field strength, the motion(s) dominating relaxation is in the long-correlation-time regime [omega 0 tau c)2 greater than 1). Thus, the gentiobiosyl headgroup undergoes the slowest motion of the glycolipid headgroups studied to date.

Calorimetry, Differential Scanning↗
PubMed1994

Solubilization of a membrane-associated protein from rat nervous system tissues which binds anionic glycolipids and phospholipids.

An anionic glycolipid and phospholipid binding protein was characterized in detergent-solubilized rat brain synaptosomes using a synthetic, polyvalent radiolabeled ganglioside-protein conjugate as radioligand. Gangliosides are prominent cell surface glycoconjugates in vertebrate brain, where they may function in membrane protein regulation or in cell-cell recognition. The neoganglioprotein (GT1b)13BSA was radioiodinated and used to probe solubilized synaptosomal proteins for ganglioside binding activity using a receptor-ligand precipitation assay. Binding data revealed a high affinity (KD = 1 nM), saturable (Bmax = 173 pmol/mg protein) binding activity that was proteinase sensitive, calcium independent and maximal at neutral pH. Size exclusion chromatography of the synaptosomal (GT1b)13BSA binding activity indicated a M(r) of approximately 28 kDa. Binding activity with similar characteristics was solubilized from other rat tissues, with activity from sciatic nerve = muscle > synaptosomes > central nervous system myelin = liver. Gangliosides added as mixed detergent-lipid micelles inhibited (GT1b)13BSA binding: GT1b, GD1a and GD1b were the most effective inhibitors (IC50 approximately 200 nM), while GM1 and GM3 were 5-fold less effective. In addition, the sphingolipids sulfatide and sialylneolactotetraosylceramide were effective inhibitors, with IC50 values of 300 nM and 200 nM, respectively. The neutral sphingolipid GA1 did not block (GT1b)13BSA binding. Phosphatidylcholine and phosphatidylethanolamine were non-inhibitory, however phosphatidylglycerol, phosphatidylserine, and phosphatidylinositol inhibited half-maximally at 200-300 nM. Inhibition by both gangliosides and anionic phospholipids was competitive with (GT1b)13BSA. We conclude that a binding protein for anionic glycolipids and phospholipids is distributed on nerve and muscle membranes.

Animals↗
PubMed1976

A sulfonolipid and novel glucosamidyl glycolipids from the extreme thermoacidophile Bacillus acidocaldarius.

The total lipid content of the extreme thermoacidophile Bacillus acidocaldarius comprises about 8.1% of the cell dry weight. Total lipid had a distribution of 15.7% neutral linique component initially characterized as an N-acylglucosamine beta-linked to the primary hydroxyl of an unusual fully saturated pentacyclic triterpene derived tetrol(C35H62O4, Mr 546), which appears to be a derivative of the pentacylcic triterpene hopane substituted at C-29 with a 1,2,3,4-tetrahydroxy pentane. Other major glycolipids present were partially characterized as O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta D-glucopyranosyldiacylglycerol and O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylmonoacylglycerol. Minor components of the glycolipid fraction included O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylglycerol, O-2-amino-2-deoxy-beta-D-glucopyranosyl pentacyclic tetrol and free pentacyclic tetrol. The distributions of esterified and amide-linked fatty acids were similar, being comprised primarily of branched heptadecanoic, 11-cyclohexyundecanoic and 13-cyclohexyltridecanoic acids. The acid lipids were composed of a sulfonoglycosyldiacylglycerol (43.2%), diphosphatidylglycerol (32.3%), lysodiphosphatidylglycerol (5.3%), phosphatidic acid (5.8%) and phosphatidylglycerol (13.4%).

Bacillus↗
PubMed1981

Biliary excretion of glycolipid in induced or inherited glucosylceramide lipidosis.

Metabolically inert L-[1-14C]glucosylceramide is stored predominantly in the liver after intravenous administration to mice. The half-time of this glycolipid analogue in the liver is 3.5 days and its clearance occurs predominantly via the bile. Within the limited number of Gaucher specimens available for examination very high levels of glucosylceramide were found in the bile of one patient and in the liver of two patients with biliary obstruction. The question of a possible relationship between biliary excretion of glycolipid and the pathogenesis of Gaucher's disease will require further studies.

Animals↗
PubMed1992

Analysis of the binding of polymyxin B to endotoxic lipid A and core glycolipid using a fluorescent displacement probe.

Dansylcadaverine, a cationic fluorescent probe binds to bacterial lipopolysaccharide and lipid A, and is displaced competitively by other compounds which possess affinity toward endotoxins. The binding parameters of dansylcadaverine for lipid A were determined by Scatchard analysis to be two apparently equivalent sites with apparent dissociation constants (Kd) ranging between 16 microM to 26 microM, while that obtained for core glycolipid from Salmonella minnesota Re595 yielded a Kd of 22 microM to 28 microM with three binding sites. The Kd of polymyxin B for lipid A was computed from dansylcadaverine displacement by the method of Horovitz and Levitzki (Horovitz, A., and Levitzki, A. (1987) Proc. Natl. Acad. Sci. USA 84, 6654-6658). The applicability of this method for analyzing fluorescence data was validated by comparing the Kds of melittin for lipid A obtained by direct Scatchard analysis, and by the Horovitz-Levitzki method. The displacement of dansylcadaverine from lipid A by polymyxin B was distinctly biphasic with Kds for polymyxin B-lipid A interactions corresponding to 0.4 microM and 1.5 microM, probably resulting as a consequence of lipid A being a mixture of mono- and di-phosphoryl species. This was not observed with core glycolipid, for which the Kd for polymyxin was estimated to range from 1.1 microM to 5.8 microM. The use of dansylcadaverine as a displacement probe offers a novel and convenient method of quantitating the interactions of a wide variety of substances with lipid A.

Binding, Competitive↗
PubMed1993

The glycolipid of Halobacterium trapanicum.

The structural elucidation of the polar lipids in Halobacterium trapanicum is reported with particular emphasis on a new sulfated disaccharide derivative of 2,3-di-O-phytanyl-sn-glycerol. The full structural designation of this glycolipid is 2,3-di-O-phytanyl-1-O- (mannopyranosyl-(2-sulfate)-alpha-D-1-2-glucopyranosyl-alpha-D)-sn-glyce rol. The value of glycolipid structures in the taxonomy of halophilic Archaea is also discussed.

Carbohydrate Sequence↗
PubMed1991

Alzheimer disease paired helical filament core structures contain glycolipid.

The core structures of sodium dodecyl sulfate extracted, pronase digested paired helical filaments of Alzheimer disease were solubilized by heating in dimethyl sulfoxide. Electron microscopy revealed that after heating in dimethyl sulfoxide, intact paired helical filaments were no longer present in the dimethyl sulfoxide soluble fractions or in the insoluble lipofuscin-containing fractions. Enzyme-linked immunosorbent assays of the various fractions with the monospecific antibody A128 to paired helical filaments demonstrated 96% of the immunoreactivity to be in the dimethyl sulfoxide soluble fraction, and only 4% in the dimethyl sulfoxide insoluble fractions. Lyophilization of the dimethyl sulfoxide soluble supernatant and resuspension in water failed to reassociate the paired helical filaments, but did result in an insoluble precipitate. Analysis of the dimethyl sulfoxide solubilized paired helical filament fraction by nuclear magnetic resonance revealed it to be composed of glycolipid in a form that was distinct from similar fractions isolated from normal aged control brains. The aggregation of an altered glycolipid to form paired helical filaments in Alzheimer disease could explain their insolubility.

Alzheimer Disease↗
PubMed1991

Glycolipid receptor binding specificity of exoenzyme S from Pseudomonas aeruginosa.

By use of the tlc overlay procedure we have shown that exoenzyme S extracted from cultures of Pseudomonas aeruginosa specifically binds to the glycolipids asialoGM1, asialoGM2 and to a lesser extent lactosyl ceramide. More significantly, strong binding was also observed to the glycerolipid receptor we have detected for Helicobacter pylori (Lancet ii, 238-241.1989). Exoenzyme S can be extracted in a toxic and nontoxic form. Toxicity correlated with ability to bind the H. pylori receptor. This species was the only receptor detected in the most sensitive cell lines. The relative binding of exoenzyme S to the ganglio series glycolipids and the glycerolipid receptor was modified in a reciprocal manner in the presence of metal ions, suggesting that exoenzyme S has two interrelated receptor binding sites.

ADP Ribose Transferases↗
PubMed1985

Glycolipid receptor for human migration inhibitory factor: fucose and sialic acid are important for the human monocyte response to migration inhibitory factor.

The role of carbohydrate in the interaction of human migration inhibitory factor (MIF) with human peripheral blood monocytes was investigated by studying the effects of different exoglycosidases on the cellular response to MIF. When monocytes were pretreated with neuraminidase, an exoglycosidase specific for sialic acid, they became unresponsive to MIF. Other glycosidases, such as beta-galactosidase and alpha-mannosidase, were inactive in this respect. The effect of neuraminidase was reversible since the response to MIF was restored to normal levels after 24 hr. In parallel studies, a glycolipid-enriched extract from U937 cells, a human macrophage-like cell line, known to enhance the monocyte response to MIF, lost this activity when treated with neuraminidase and alpha-L-fucosidase, but not with beta-galactosidase. This suggests the importance of terminal sialic acid and fucose residues for the interaction between monocyte membrane glycolipids and MIF.

Cell Line↗
PubMed1980

Synthesis of glycolipids.

The chemical syntheses of naturally occurring glycolipids derived from sphingosine bases and glycerol derivatives, and the syntheses of polyisoprenoid lipid intermediates and other miscellaneous glycolipids recorded up to the end of 1977 are reviewed.

Ceramides↗
PubMed1985

The allyl group for protection in carbohydrate chemistry. 17. Synthesis of propyl O-(3,6-di-O-methyl-beta-D-glucopyranosyl)-(1----4)-O-(2,3- di-O-methyl-alpha-L-rhamnopyranosyl)-(1----2)-3-O-methyl-alpha- L-rhamnopyranoside: the oligosaccharide portion of the major serologically active glycolipid from Mycobacterium leprae.

Allyl 4-O-benzyl-alpha-L-rhamnopyranoside was converted into allyl 4-O-benzyl-3-O-methyl-alpha-L-rhamnopyranoside and this was condensed with 2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl chloride to give a disaccharide derivative which was converted into allyl 4-O-benzyl-2-O-(2,3-O-isopropylidene-alpha-L-rhamnopyranosyl)-3-O-methyl -alpha- L-rhamnopyranoside. This disaccharide derivative was condensed with 2,4-di-O-acetyl-3,6-di-O-methyl-alpha-D-glucopyranosyl chloride to give a trisaccharide derivative which was converted into the title compound. This compound represents the oligosaccharide portion of the major serologically active glycolipid from Mycobacterium leprae which is required to prepare a synthetic diagnostic agent for leprosy infection at an early stage and to investigate the specificities of monoclonal antibodies directed towards the glycolipid.

Glycolipids↗
PubMed1988

N-pyrene dodecanoyl sulfatide as membrane probe: a study of glycolipid dynamic behavior in model membranes.

An N-linked pyrene-dodecanoyl sulfatide was employed to measure the ratio of excimer fluorescence to monomer fluorescence intensities (E/M). The E/M values provided information about both the dynamic behavior and the structural distribution of the labelled glycolipid in note dispersion of micellar sulfatides and multilamellar vesicles of different phospholipids. Most of the labelled sulfatide seems to be located in domains sequestered from the surrounding phospholipids still above the phase transition temperature of the vesicles. The glycolipids sequestered in these domain environments are less sensitive to the structural changes that the addition of cholesterol or Ca2+ can induce in the phospholipid regions during the phase transition.

Fluorescent Dyes↗