Carbohydrate composition and sequence analysis of a derivative of brain disialoganglioside by mass spectrometry, with molecular weight ions at m-e 2245. Potential use in the specific microanalysis of cell surface components

Helicobacter pylori and complex gangliosides

Recognition of sialic acid-containing glycoconjugates by the human gastric pathogen Helicobacter pylori has been repeatedly demonstrated. To investigate the structural requirements for H. pylori binding to complex gangliosides, a large number of gangliosides were isolated and characterized by mass spectrometry and proton nuclear magnetic resonance. Ganglioside binding of sialic acid-recognizing H. pylori strains (strains J99 and CCUG 17874) and knockout mutant strains with the sialic acid binding adhesin SabA or the NeuAcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta-binding neutrophil-activating protein HPNAP deleted was investigated using the thin-layer chromatogram binding assay. The wild-type bacteria bound to N-acetyllactosamine-based gangliosides with terminal alpha3-linked NeuAc, while gangliosides with terminal NeuGcalpha3, NeuAcalpha6, or NeuAcalpha8NeuAcalpha3 were not recognized. The factors affecting binding affinity were identified as (i) the length of the N-acetyllactosamine carbohydrate chain, (ii) the branches of the carbohydrate chain, and (iii) fucose substitution of the N-acetyllactosamine core chain. While the J99/NAP(-) mutant strain displayed a ganglioside binding pattern identical to that of the parent J99 wild-type strain, no ganglioside binding was obtained with the J99/SabA(-) mutant strain, demonstrating that the SabA adhesin is the sole factor responsible for the binding of H. pylori bacterial cells to gangliosides.

Novel carbohydrate binding site recognizing blood group A and B determinants in a hybrid of cholera toxin and Escherichia coli heat-labile enterotoxin B-subunits

The B-subunits of cholera toxin (CTB) and Escherichia coli heat-labile enterotoxin (LTB) are structurally and functionally related. However, the carbohydrate binding specificities of the two proteins differ. While both CTB and LTB bind to the GM1 ganglioside, LTB also binds to N-acetyllactosamine-terminated glycoconjugates. The structural basis of the differences in carbohydrate recognition has been investigated by a systematic exchange of amino acids between LTB and CTB. Thereby, a CTB/LTB hybrid with a gain-of-function mutation resulting in recognition of blood group A and B determinants was obtained. Glycosphingolipid binding assays showed a specific binding of this hybrid B-subunit, but not CTB or LTB, to slowly migrating non-acid glycosphingolipids of human and animal small intestinal epithelium. A binding-active glycosphingolipid isolated from cat intestinal epithelium was characterized by mass spectrometry and proton NMR as GalNAcalpha3(Fucalpha2)Galbeta4(Fucalpha3)Glc NAcbeta3Galbeta4Glc NAcbeta3Galbeta4Glcbeta1Cer. Comparison with reference glycosphingolipids showed that the minimum binding epitope recognized by the CTB/LTB hybrid was Galalpha3(Fucalpha2)Galbeta4(Fucalpha3)GlcNAc beta. The blood group A and B determinants bind to a novel carbohydrate binding site located at the top of the B-subunit interfaces, distinct from the GM1 binding site, as found by docking and molecular dynamics simulations.

Analysis of 3- and 6-linked sialic acids in mixtures of gangliosides using blotting to polyvinylidene difluoride membranes, binding assays, and various mass spectrometry techniques with application to recognition by Helicobacter pylori

A convenient approach to analyze 3- and 6-linked sialic acids in mixtures of biologically active gangliosides was developed. The procedure was adapted to work on small amounts of material and included parallel tests, which allowed direct analysis of structure and activity. The initial step in the procedure was separation of a mixture of gangliosides by thin-layer chromatography (TLC) and blotting to a polyvinylidene difluoride membrane. The gangliosides were then analyzed (a) by direct desorption from the membrane and fast atom bombardment mass spectrometry (FAB MS), (b) by membrane-binding assay using the NeuAcalpha3- and NeuAcalpha6-specific lectins from Maackia amurensis and Sambucus nigra, respectively, and (c) by TLC binding assay with radiolabeled bacteria. All experiments were performed on a mixture of gangliosides from human leucocytes, which contained species with affinity for the human gastric pathogen Helicobacter pylori. The procedure was used with good results for gangliosides with up to seven sugars per ceramide. A three-sugar ganglioside was identified as GM3 with ceramides composed of sphingosine (d18:1) and 20:0, h20:0, and 24:0 fatty acids. The sequences of four bands in the five-sugar region were consistent with sialylparagloboside (NeuAcalpha3/6Galbeta4GlcNAcbeta3Galbeta4GlcbetaCer). The ceramides were composed of d18:1 and 24:1 fatty acid in the first and third bands, and d18:1 and 16:0 fatty acid in the second and fourth bands from the top. The sialic acid was shown to be 3-linked in the upper two bands and 6-linked in the lower two bands. The same distribution of sialic acid and ceramides but the sequence elongated with one N-acetyllactosamine unit was observed in the less resolved interval containing seven-sugar glycosphingolipids. The direct comparison of binding of lectins and radiolabeled bacteria showed that H. pylori recognized 3-linked sialic acid only. These results were supported by a novel technique of analysis of the sialic acid linkage position by trifluoroacetolysis and gas chromatography/MS. Direct membrane/FAB MS was ineffective for species migrating below the seven-sugar region on the TLC. In this case, the membranes were instead cut in bands and the gangliosides extracted by methanol before analysis by FAB MS.

Selective binding by Helicobacter pylori of leucocyte gangliosides with 3-linked sialic acid, as identified by a new approach of linkage analysis

The human gastric pathogen Helicobacter pylori has been shown to bind to glycoconjugates of human leucocytes in a sialic acid-dependent way. In order to improve the identification of the binding epitope, a new technique was developed to analyze the ketosidic linkage position between a terminal sialic acid and the consecutive monosaccharide. Permethylation and reduction with LiAlH4 followed by trifluoroacetolysis in 1000:1 trifluoroacetic anhydride:trifluoroacetic acid (24 h, 100 degrees C) results in the cleavage of glycosidic but not ketosidic bonds. The disaccharide products were analyzed by gas chromatography-mass spectrometry and sialyl-3 or -6 position and NeuAc or NeuGc are identified by their separate retention times and mass spectra. The method was worked out on model saccharides and applied on five-sugar gangliosides (sialylparaglobosides) of human leucocytes. Radiolabeled Helicobacter pylori was shown to bind to the upper part, but not to the lower part, of the five-sugar interval of a mixture of gangliosides separated on a thin-layer chromatogram. Using a membrane blotting procedure the active and inactive bands were isolated and shown to be NeuAcalpha2-3- and NeuAcalpha2-6-paraglobosides, respectively.

The lactosylceramide binding specificity of Helicobacter pylori

The possible role of glycosphingolipids as adhesion receptors for the human gastric pathogen Helicobacter pylori was examined by use of radiolabeled bacteria, or protein extracts from the bacterial cell surface, in the thin-layer chromatogram binding assay. Of several binding specificities found, the binding to lactosylceramide is described in detail here, the others being reported elsewhere. By autoradiography a preferential binding to lactosylceramide having sphingosine/phytosphingosine and 2-D hydroxy fatty acids was detected, whereas lactosylceramide having sphingosine and nonhydroxy fatty acids was consistently nonbinding. A selective binding of H. pylori to lactosylceramide with phytosphingosine and 2-D hydroxy fatty acid was obtained when the different lactosylceramide species were incorporated into liposomes, but only in the presence of cholesterol, suggesting that this selectivity may be present also in vivo . Importantly, lactosylceramide with sphingosine and hydroxy fatty acids does not bind in this assay. Furthermore, a lactosylceramide-based binding pattern obtained for different trisaccharide glycosphingolipids is consistent with the assumption that this selectivity is due to binding of a conformation of lactosylceramide in which the oxygen of the 2-D fatty acid hydroxyl group forms a hydrogen bond with the Glc hydroxy methyl group, yielding an epitope presentation different from other possible conformers. An alternative conformation that may come into consideration corresponds to the crystal structure found for cerebroside, in which the fatty acid hydroxyl group is free to interact directly with the adhesin. By isolating glycosphingolipids from epithelial cells of human stomach from seven individuals, a binding of H.pylori to the diglycosylceramide region of the non-acid fraction could be demonstrated in one of these cases. Mass spectrometry showed that the binding-active sample contained diglycosylceramides with phytosphingosine and 2-D hydroxy fatty acids with 16-24 carbon atoms in agreement with the results related above.

Generation of a murine monoclonal antibody specific for N-glycolylneuraminic acid-containing gangliosides that also recognizes sulfated glycolipids

The P3 murine monoclonal antibody (MAb) was generated by immunizing BALB/c mice with NeuGcGM3 included into liposomes. The specificity of this MAb was defined by an enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatograms. P3 MAb binds to NeuGc-containing gangliosides and was shown also to react with sulfated glycolipids. A preliminary immunohistochemical study showed that the P3 MAb was able to recognize antigens expressed in human breast tumors.

Structural and immunochemical identification of Leb glycolipids in the plasma of a group O Le(a-b-) secretor

Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Le(c)), H type 1 (Le(d)), Le(a) and Le(b) epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc alpha 1-2Gal beta 1-3GlcNac beta 1-3Gal beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Le(b) blood group glycolipids (Fuc alpha 1-2Gal beta 1-3(Fuc alpha 1-4)GlcNAc beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals.

Structure and genetic polymorphism of blood group A-active glycosphingolipids of the rat large intestine

Study of blood group A- and B-active glycosphingolipid content of the epithelium of the large intestine of 16 strains of inbred rats led to the discovery of two related strains, SHR and WKY, devoid of A-active glycolipids, whereas all strains expressed B-active glycolipids. This finding evidenced a new A/non-A genetic polymorphism in the rat. Blood group A-active glycolipids were isolated from the large intestine of F344 rats and purified by affinity chromatography on immobilized Helix pomatia lectin. Three glycolipid fractions were separated by preparative thin-layer chromatography and characterized by electron-impact mass spectrometry of their permethylated and permethylated-LiAlH4-reduced derivatives. They were identified as a tetraglycosylceramide (A-4), a hexaglycosylceramide (A-6), and a difucosylated heptaglycosylceramide (A-7) with small amounts of monofucosylated octaglycosylceramide (A-8). Methylation analysis and fragmentation indicated that A6 and A-8 had a lacto- and A-7 a neolactotetraosylceramide core, respectively, identical to the core structures of B-6 and B-7 previously characterized in the large intestine of WF rats (Angström et al. (1987) Biochim. Biophys. Acta 926, 79-86). Upon methylation analysis, B-6 and B-7 purified from SHR (A-deficient) and F344 (A-expressing) were found identical to those of WF rats. This result indicated that precursor substrates for the synthesis of A-active glycolipids were available in SHR rats and thus the genetic deficiency of A-active glycolipid expression probably originated in a defect of the termination of the blood group A determinant by the alpha-3-N-acetylgalactosaminyltransferase.

Comparison of the glycolipid-binding specificities of cholera toxin and porcine Escherichia coli heat-labile enterotoxin: identification of a receptor-active non-ganglioside glycolipid for the heat-labile toxin in infant rabbit small intestine

The binding specificities of cholera toxin and Escherichia coli heat-labile enterotoxin were investigated by binding of 125I-labelled toxins to reference glycosphingolipids separated on thin-layer chromatograms and coated in microtitre wells. The binding of cholera toxin was restricted to the GM1 ganglioside. The heat-labile toxin showed the highest affinity for GM1 but also bound, though less strongly, to the GM2, GD2 and GD1b gangliosides and to the non-acid glycosphingolipids gangliotetraosylceramide and lactoneotetraosylceramide. The infant rabbit small intestine, a model system for diarrhoea induced by the toxins, was shown to contain two receptor-active glycosphingolipids for the heat-labile toxin, GM1 ganglioside and lactoneotetraosylceramide, whereas only the GM1 ganglioside was receptor-active for cholera toxin. Preliminary evidence was obtained, indicating that epithelial cells of human small intestine also contain lactoneotetraosylceramide and similar sequences. By computer-based molecular modelling, lactoneotetraosylceramide was docked into the active site of the heat-labile toxin, using the known crystal structure of the toxin in complex with lactose. Interactions which may explain the relatively high toxin affinity for this receptor were found.

Electron ionization-tandem mass spectrometry of glycosphingolipids. Part II. The identification of a carbohydrate sequence corresponding to a novel repetitive blood group A heptaglycosylceramide

In a previous paper, the presence in human kidney vein tissue of a novel blood group A heptaglycosylceramide based on the type-3 carbohydrate chain GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta 1-3GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta 1-4Glc beta 1-1 Ceramide, was suggested based on thin-layer immunostaining and electron ionization mass spectrometry. Ions corresponding to a structure containing two deoxyhexoses, two hexosamines and three hexoses were identified, but no information was obtained from mass spectrometry concerning the carbohydrate sequence. In the present paper, we report the identification of carbohydrate sequence ions corresponding to a type-3 chain A heptaglycosylceramide by electron ionization-tandem mass spectrometry of a permethylated-reduced glycosphingolipid mixture isolated from human kidney vein tissue. The use of a microchannel-plate-array detector increased the sensitivity for collision-induced dissociation spectra by a factor of at least ten over a conventional electron multiplier.

Glycosphingolipid expression in spontaneously aborted fetuses and placenta from blood group p women. Evidence for placenta being the primary target for anti-Tja-antibodies

A 12-week-old fetus and one 17-week-old fetus + placenta were obtained after spontaneous abortions from two women of blood group p. The 17-week-old fetus was dissected into intestine, liver, brain and residual tissue. Nonacid glycosphingolipid fractions were prepared from the tissues. Glycolipid characterization was carried out using thin layer chromatography immunostained with monoclonal antibodies and bacteria and by 1H NMR spectroscopy and mass spectrometry. In the placental fraction substantial amounts of globotetraosylceramide (P-antigen) and globotriaosylceramide (Pk-antigen) were identified. In contrast, the fetuses contained only trace amounts of these structures, as revealed by immunostaining. These results indicate that the primary target for the antibodies of the anti-Tja serum is the placenta tissue, resulting in termination of the pregnancy.

Electron ionization-tandem mass spectrometry of glycosphingolipids. I: The identiftcation of compound-specific sequence ions in the collision-induced dissociation spectra of the immonium ions of two isomeric hexaglycosylceramides

A permethylated-reduced hexaglycosylceramide in a complex glycolipid mixture isolated from a unique human tissue has been identified by using tandem mass spectrometry (MS/MS). The mass spectrum of this glycolipid mixture, obtained by using in-beam electron ionization, is very complex, and fragment ions derived from the hexaglycosylceramide cannot be distinguished from other ions. Tandem mass spectrometry using a four-sector mass spectrometer gave the mass spectrum of the immonium ion of the permethylated-reduced hexaglycosykeramide (m / z 1645.8), which is characteristic of its structure. Comparison of this MS/MS spectrum with those of two similarly derivatized blood group hexaglycosylceramide isomers permitted identification of the unknown glycolipid structure.

The resolution into molecular species on desorption of glycolipids from thin-layer chromatograms, using combined thin-layer chromatography and fast-atom-bombardment mass spectrometry

Using a specially designed, motorised t.l.c.-f.a.b.-m.s. probe with continuous desorption and scanning over a moving t.l.c. plate, it was shown that glycolipids with identical carbohydrate sequences were well resolved into molecular species with differences in long-chain base and fatty acid. There was no serious diffusion of the glycolipids into the matrix. The technique is demonstrated for sulphatides (one and two sugar residues) isolated from human kidney, GM3 ganglioside isolated from human malignant melanoma, and chemically modified gangliotetraosylceramide from mouse intestine. T.l.c.-f.a.b.m.s. is convenient for sequencing and composition analysis of receptor-active glycolipids, the biological activity of which can be monitored in parallel by overlay on the t.l.c. plate with proteins, viruses, bacteria, or animal cells.

Blood group type glycosphingolipids of human kidneys. Structural characterization of extended globo-series compounds

Blood group type glycosphingolipids present in kidneys of blood group A and B human individuals have been isolated and structurally characterized by mass spectrometry, proton NMR spectroscopy, degradation studies and by their reactivity with various monoclonal antibodies and Escherichia coli bacteria. The two major complex glycolipids present in the blood group A and B kidneys were globopentaosylceramide (IV3Gal beta-Gb4Cer) and the X pentaglycosylceramide (III3Fuc alpha-nLc4Cer). The major blood group A glycolipid in the blood group A kidneys was based on the type 4 chain (globo-series). There were also small amounts of the type 2 chain and trace amounts of the type 1 and type 3 chain based A glycolipids. In addition, the blood group H type 4 chain structure was present together with Le(a) and Le(b) compounds. In the blood group B kidneys, the major B glycolipids were monofucosylated hexa- and octaglycosylceramides, where the former were based on the type 2 carbohydrate chain. The blood group B type 4 chain heptaglycosylceramide was found to be a minor component making up only about 1% of the total blood group B structures.

Strategies for characterization of ganglioside inner esters. I--Fast atom bombardment mass spectrometry

A comparison of old and new fast atom bombardment (FAB) mass spectrometric strategies for characterization of ganglioside inner esters (lactones) is presented. Data obtained for lactones of GD3 (NeuAc alpha 2----8NeuAc alpha 2----3Gal beta 1----4Glc beta 1----1Cer) using negative ion FAB mass spectrometry of underivatized materials, negative ion FAB mass spectrometry following ammonolysis, and positive ion FAB mass spectrometry following ammonolysis and permethylation are presented and discussed. The latter method uses well-known reactions to produce a novel type of ganglioside derivative, highly amenable to analysis by positive ion FAB mass spectrometry, which is introduced to simplify unambiguous location of NeuAc residues involved in ester linkages to other sugars.

Analysis of derivatized ceramides and neutral glycosphingolipids by high-performance tandem mass spectrometry

Microscale reduction of ceramides and neutral glycosphingolipids has been evaluated as a means of improving their analysis by fast atom bombardment mass spectrometry, alone and in combination with tandem mass spectrometry. Reduction (conversion of the amide to an amine) of native ceramides and glycosphingolipids containing one to three sugars yields derivatives that show significant signal enhancement. This sensitivity increase allows the acquisition of normal and tandem fast atom bombardment mass spectra from a submicrogram amount of sample. Concomitant permethylation is required for glycosphingolipids that contain more than three sugars. Collision induced dissociation mass spectra of protonated molecular ions, recorded on a four sector instrument, show improved fragmentation allowing the simultaneous characterization of both the ceramide and carbohydrate portions of glycosphingolipids. The reductions are carried out at the nanogram to microgram level with borane, reacting the solid sample with condensed reagent vapor. The borane reduction method has been adapted for this class of substances by adding an oxidation step in order to convert unsaturated lipids to hydroxylated derivatives by oxidation of the resulting organoborane. This approach, used in conjunction with tandem mass spectrometry, allows the determination of olefinic bond location. Labeled derivatives have been prepared by reacting the substrates with trideuterioborane and were used to ascertain the fragmentations and localize olefinic bonds. The collision induced fragmentation of reduced ceramides and neutral glycosphingolipids is only weakly affected by the presence of additional functionalities, such as methoxyl (after permethylation) and hydroxyl groups (resulting from hydroboration and oxidation), a characteristic which facilitates interpretation of the spectra of unknown compounds.

Intestinal-type glycosphingolipids in urine from patients with enterocutaneous urinary diversions

Ureteroenterocutaneous stoma is a surgical procedure for urinary diversion by which an intestinal segment is used as a conduit or reservoir for the urine. The intestinal mucosa continues to produce a mucous gel containing desquamated epithelial cells. This mucous gel is easily obtainable from the urine. Glycosphingolipids were isolated from such gels and analyzed with immunological methods using a thin-layer chromatography overlay assay and mass spectrometry. The glycosphingolipids obtained mainly belong to the lacto-type I series comprising ABH, Lea, and Leb determinants. These observations support the intestinal origin of the glycosphingolipids. A regional distribution of the ABH and Lewis antigens, which is in accordance with previous immunohistochemical findings, was observed.

Continuous-flow fast atom bombardment-mass spectrometry of permethylated oligosaccharides: a comparative study of direct mixture analysis with packed capillary column liquid chromatography-fast atom bombardment-mass spectrometry

Conventional positive fast atom bombardment (FAB) and continuous-flow FAB analysis were carried out with permethylated lacto-N-tetraose. This latter method, a new approach, has been used to analyze a mixture of permethylated oligosaccharides by liquid chromatography-mass spectrometry (LC-MS) with a packed capillary fused-silica column and the continuous-flow probe as interface. Under these conditions, we found the continuous-flow probe to be superior to the conventional probe because its low matrix level increased the signal-to-noise ratio. The analysis of the mixture of permethylated oligosaccharide alditols obtained from hen ovomucoid by LC-MS using the continuous-flow probe as interface is described.

The glycosphingolipid composition of the placenta of a blood group P fetus delivered by a blood group Pk1 woman and analysis of the anti-globoside antibodies found in maternal serum

To further define the molecules that may mediate spontaneous abortion due to maternal-fetal blood group incompatibility within the P blood group system, we have examined the fine specificities of maternal antibodies and the glycolipid antigens from the placenta of a P infant born to a Pk1 mother. Maternal antibodies obtained during therapeutic plasmapheresis were analyzed to determine their reactivities with placental glycolipid extracts on thin-layer plates. Second antibodies specific for IgM, IgG, and IgA revealed immunoglobulins of all of these classes strongly reactive with one major placental glycolipid that comigrates with globoside. GC/MS analysis confirmed that the major P-active pentaglycosylceramide of placenta has the same structure as that previously shown for the P antigen of red blood cells: GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-Cer. Serum antibodies partially purified by affinity chromatography on globoside-octyl-Sepharose specifically recognize glycolipids that contain terminal GalNAc beta 1-3Gal . . . residues and also recognize the same sequence as an internal determinant in some, but not all, glycolipids with extended globoside core regions. Thus, in the blood group P incompatible fetus, the major P antigen present in placenta has the same carbohydrate structure as the P antigen present in fetal and adult erythrocytes and might be a target for the maternal immune system.

The mono- and difucosyl blood group B glycosphingolipids of rat large intestine differ in type of core saccharide

Two blood group B-active glycosphingolipids were isolated from rat large intestine and characterized by mass spectrometry, proton NMR spectroscopy and methylation analysis. The following structures were concluded: Gal alpha 1----3(Fuc alpha 1----2)Gal beta 1----3GlcNAc beta 1----3Gal beta 1----4Glc beta 1----1Cer and Gal alpha 1----3(Fuc alpha 1----2)Gal beta 1----4(Fuc alpha 1----3)GlcNAc beta 1----3Gal beta 1----4Glc beta 1----1Cer. The two glycolipids thus differ in their core saccharides (type 1 and type 2 chain, respectively) and therefore must have different pathways for biosynthesis.

Application of a simple methylation procedure for the analyses of glycosphingolipids

Acid and neutral glycosphingolipids (0.01-1 mumol) were completely methylated in high yields and with little formation of by-products in 10 min at room temperature, using methyl sulphoxide, methyl iodide, and powdered NaOH. Re-methylation of methylated and LiAlH4-reduced gangliosides gave a new derivative that was useful for the analysis of gangliosides by mass spectrometry.

GalNAc beta 1----3 terminated glycosphingolipids of human erythrocytes

Nonacid glycosphingolipids with 4 to 10 sugar residues isolated from pooled erythrocytes of blood group O donors have been efficiently separated as peracetylated derivatives on silicic acid. This procedure enabled a quantitative estimate of individual compounds and also revealed several GalNAc beta 1----3 terminated structures. The structural characterization of these glycolipids with 1H-NMR spectroscopy, direct inlet mass spectrometry, gas chromatography, and gas chromatography-mass spectrometry identified the compounds as GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1-N-acetyl sphingosine and GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1-N-acetyl phytosphingosine, GalNAc beta 1----3GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1 ceramide, and GalNAc beta 1----3Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4Glc beta 1----1 ceramide.

Globoseries glycosphingolipids of human meconium

Globoside and an extended globoseries glycosphingolipid with a blood group H determinant were isolated from pooled human meconia and structurally characterized by mass spectrometry, proton NMR spectroscopy, and degradational techniques using GC and GC-MS analyses. Both species contained mainly phytosphingosine and hydroxy fatty acids characteristic for human intestinal epithelial cells. With the same techniques also minor amounts of globoside with sphingosine and nonhydroxy fatty acids and a novel globoseries tetraglycosyl ceramide with a terminal N-acetylglucosamine were isolated and structurally characterized.

Two strains of the Madin-Darby canine kidney (MDCK) cell line have distinct glycosphingolipid compositions

The glycosphingolipids (GSLs) of two sublines of Madin-Darby canine kidney (MDCK) cells, an epithelial cell line, were characterized by t.l.c., antibody overlay and mass spectrometry. The major characteristic which distinguishes the two MDCK cell strains is their trans-epithelial electrical resistance which is typically of the order of 3000 ohm.cm2 for strain I and 100 ohm.cm2 for strain II cells. Strain I and II cells were equally rich in glycolipids, the cellular GSL/phospholipid ratio being 0.04. However, while the phospholipid patterns were identical, the GSLs showed striking differences, and each cell strain expressed appreciable amounts of GSLs that were not found in the other strain. Both cell types possessed neutral GSLs with one, two or three carbohydrate moieties. The monoglycosylceramide accounted for 50% of the total GSLs in each strain. However, while in strain I cells over 90% of this monoglycosylceramide was monoglucosylceramide, in strain II cells over 90% consisted of monogalactosylceramide. In addition, MDCK strain II cells selectively expressed GSLs belonging to the globo series (26% of its neutral GSLs), including globoside and Forssman antigen, a globoside derivative. MDCK strain I cells, on the other hand, expressed another series of GSLs with 4-7 carbohydrate moieties characterized by the common sequence Hex-HexNAc-Hex-Hex-Cer. The presence of two fucosylated GSLs in these series was established. Both MDCK strain I and II cells contained negatively charged GSLs, the major component of which was the ganglioside GM3. MDCK strain II cells in addition expressed sulfatide, the sulfated derivative of galactosylceramide.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural characterization of glycosphingolipids by direct chemical ionization mass spectrometry

This report describes the use of direct chemical ionization mass spectrometry with ammonia as the reagent gas (NH3-DCI) for structure analysis of underivatized, permethylated and permethylated and reduced glycosphingolipids. In contrast to ionization by electron impact, the NH3-DCI mass spectra exhibit intense molecular and carbohydrate sequence-related ions using microgram amounts of sample. Underivatized glycosphingolipids with up to two sugar residues yield abundant protonated and ammonia-cationized molecular ions and structurally significant fragments. Permethylation in conjunction with NH3-DCI can be used to obtain molecular weight as well as oligosaccharide sequence and branching information on neutral, acidic and complex-type glycosphingolipids with up to five sugar residues. Reduction of the permethylated derivatives gives rise to several new, structurally significant fragments in the corresponding NH3-DCI mass spectra which enable fatty acid and base compositions to be determined. Isotopically labeled reagent gases have been used to confirm the assignment of fragment structures and to demonstrate that the ions observed are unique to the NH3-DCI mass spectra.

Electron ionization mass spectra of reduced and permethylated urinary oligosaccharides from patients with mannosidosis

The electron ionization mass spectra of reduced and permethylated isomeric mixtures of the major urinary tri- to deca-oligosaccharides of patients with mannosidosis are reported. Many of the oligosaccharide isomers can be differentiated in the mixtures on the basis of their distinct fragmentation patterns.

Glycosphingolipid patterns of the epithelial and non-epithelial compartments of rat large intestine

The epithelial cells and the non-epithelial residue from large intestine of two inbred rat strains were separated and the glycosphingolipids characterized in comparison with earlier detailed data from small intestine of the same strains. Total acid and non-acid glycolipids were prepared and the non-acid glycolipids were further fractionated into subgroups as acetylated derivatives on silicic acid. The fractions obtained were characterized mainly by thin-layer chromatography, including binding of monoclonal anti-A and anti-B antibody to the chromatogram, and by direct-inlet mass spectrometry after derivatization. This combined technology allowed an overall conclusion from a small number of animals concerning relative amounts of glycolipids, microheterogeneity of blood group glycolipids and carbohydrate sequence and lipophilic components of major species of each subfraction. As for the small intestine, the two separated compartments differed distinctly in composition, with blood group fucolipids being confined to the epithelial cells, and a series of glycolipids with probably internal Gal alpha being restricted to the non-epithelial part. The main difference between large and small intestine concerned fucolipids of the epithelium. Three blood group B active glycolipids with four, six and seven sugars were detected which were absent from the small intestine. The four-sugar glycolipid was a major glycolipid with the structure Gal alpha 1----3Gal(2----1 alpha Fuc) beta 1----4Glc beta 1----1Cer. as reported before. The six-sugar glycolipid was shown by mass spectrometry and NMR spectroscopy to have the probable structure Gal alpha 1----3Gal(2----1 alpha Fuc)beta 1----3GlcNAc beta 1----3Gal beta 1----4Glc beta 1----1Cer. The seven-sugar glycolipid had an additional fucose linked to N-acetylhexosamine, as shown by mass spectrometry. Three blood group A active glycolipids with four, six and seven sugars were found in both rat strains, with sequences analogous to the B glycolipids but with a terminal GalNAc instead of Gal. The four- and six-sugar blood group A compounds, but not the seven-sugar glycolipid, have been found before in the small intestine of one of the rat strains. In the small intestine, on the other hand, a branched-chain twelve-sugar blood group A active glycolipid has been found which was absent from the large intestine. Therefore large intestine of both rat strains expressed glycolipid-based blood group A and B activity, while small intestine lacked B activity and showed A activity only in one of the strains.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical-ionization mass spectra of the permethylated sialo-oligosaccharides liberated from gangliosides

Permethylated mono- and di-sialo-oligosaccharides liberated from several parent gangliosides have been examined by chemical-ionization mass spectrometry with ammonia as the reagent gas in order to elucidate their structures. Several major fragment-ions, in addition to both the protonated and ammonium adduct molecular-ions, may be readily assigned without interference from the ceramide moiety. Sialic acid-containing di-, tri-, and tetra-saccharide ions can be clearly observed and used to determine the sugar residue to which the sialic acid residue is attached. The neutral-sugar skeletons produced by the loss of sialic acid give rise to both the protonated and the ammonium adduct ions; in the case of tetrasaccharides, these are further degraded to produce di- and tri-saccharide ions. These characteristic ions are useful for the determination of the number of sugar residues and their sequence in an oligosaccharide structure. The chemical-ionization mass spectra of GM3- and GM1-oligosaccharides with isobutane show the ions corresponding to each monosaccharide residue. These results indicate that chemical-ionization mass spectrometry is highly useful in determining the complete sugar-sequence of gangliosides.

Tissue specificity of glycosphingolipids as expressed in pancreas and small intestine of blood group A and B human individuals

A chemical investigation has been done on blood group active glycosphingolipids of both small intestine and pancreas from two individuals, one blood group A and one blood group B. Total non-acid glycolipid fractions were prepared and the major blood group fucolipids present were purified and structurally characterized by mass spectrometry, proton NMR spectroscopy, and degradation methods. The glycolipid structures identified were a blood group Leb hexaglycosylceramide, a B-hexaglycosylceramide with a type 1 (Gal beta 1 leads to 3GlcNAc) carbohydrate chain, A-hexaglycosylceramides with types 1 and 2 (Gal beta 1 leads to 4GlcNAc) carbohydrate chains, a B-heptaglycosylceramide with a type 1 carbohydrate chain, and A-heptaglycosylceramides with type 1 and 2 carbohydrate chains. In addition several minor glycolipids having more than seven sugar residues were detected by thin-layer chromatography. The small intestine and pancreas had some distinct differences in their expression of the major fucolipids. The small intestine contained only glycolipids based upon type 1 carbohydrate chain while the pancreas had both type 1 and type 2 structures. The intestines contained mainly difucosyl compounds while the pancreas tissues contained both mono- and difucosyl glycolipids. Monofucosylglycolipids based on both types 1 and 2 saccharides were present in one pancreas while the other one contained only monofucosylcomponents based on type 1 chain. The ceramides of the intestinal glycolipids were found to be more hydroxylated (trihydroxy long-chain base, hydroxy fatty acids) compared to the pancreas glycolipids (dihydroxy long-chain base, non-hydroxy fatty acids).