Sialic Acid Units Research Articles

Isolation, biochemical and immunological characterisation of two sea urchin glycoproteins bearing sulphated poly(sialic acid) polysaccharides rich in N-glycolyl neuraminic acid

Two different sialoproteins were isolated from the sea urchin shell by guanidine hydrochloride extraction in the presence of Triton X-100. The sialoproteins (SP I and SP II) were purified on DEAE-Sephacel and Sepharose CL-6B and separated from each other by density gradient centrifugation. The ratio between recovered SP I and SP II was 1:4.5 and their M rs 650 and 600 kDa, respectively. They were degraded by neuraminidase, endoglycosidase F and peptide N-glycosidase F resulting in fragments of similar relative molecular mass ( M rs). Although their protein cores have approximately the same relative molecular mass of 500 kDa, they differ markedly in their contents of aspartic acid/asparagine, glycine, leucine and phenylalanine, as well as in the primary amino acid sequence of their N-terminal peptides. Carbohydrate analyses showed that the sialic acid content was higher in SP I (11.4% of dry tissue weight) than in the more prominent SP II (5.3%). Two types of carbohydrates, O-glycosidally-linked polysaccharides and N-glycosidically-linked oligosaccharides are present in both sialoproteins. SP I contains 10–11 polysaccharides chains whereas SP II contains 5–6. The polysaccharides are linked to protein cores via galactosamine, have approximately the same M r of 12 kDa and contain 32–33 N-glycolyl neuraminic acid, 10–11 glucosamine, 6–7 sulphate and 6–8 neutral monosaccharide residues. Sialic acid residues ar organized in a poly(sialic acid) unit which is present in the non-reducing terminal of the polysaccharides and degraded by neuraminidase. Hexosamines, sulphates and neutral monosaccharides are all constituents of the sialic acid free region of the chain near the reducing end. Two oligosaccharide populations were isolated from SP I, one major (70% of the total oligosaccharides) with M r of approximately 3 kDa and the other with M r of 1.5 kDa. In SP II, however, only a 3-kDa oligosaccharide population was present. The oligosaccharides from both sialoproteins are N-glycosidically linked to asparagine via the glycosamine and contain mannose, glucosamine, galactosamine, and sialic acids. Antibodies against SP II were raised in rabbits and it was shown that the antigenicity of SP II was lost on either neuraminidase or trypsin digestion, indicating that both the poly(sialic acid) units of the polysaccharide and the protein core are antigenically active. As expected, SP II showed considerable cross-reactivity with SP I due to the common poly(sialic acid) structure. There were no significant reactivities of SP II and SP I with antibodies to bovine bone sialoprotein and osteopontin. The biological role of the two sea urchin sialoproteins as developmentally regulated products of the tissue remains to be elucidated.

The ability to re-express polysialylated NCAM in soleus muscle after denervation is reduced in aged rats compared to young adult rats

The neural cell-adhesion molecule, NCAM, contains an unusual homopolymer of sialic acid units, polysialic acid. This carbohydrate seems to be involved in neurite outgrowth, bundling and branching, processes which are important during reinnervation. In aged rats, reinnervation of denervated muscle fibres is incomplete. In this study, age-related changes in the degree of polysialylation of NCAM re-expressed after denervation were examined using a monoclonal antibody recognizing polysialic acid and a polyclonal antibody recognizing NCAM. The results show that, after denervation, the degree of polysialylation on NCAM was clearly reduced in rat soleus muscle of aged, compared to young, adult rats. This age-related change in expression of polysialic acid probably influences the reinnervation process in aged muscle.

Synthetic Studies on Sialoglycoconjugates 60: α-Stereocontrolled, Glycoside Synthesis of Trimeric Sialic Acid with Galactose and Lactose Derivatives

Abstract α-Stereocontrolled, glycoside synthesis of trimeric sialic acid is described toward a systematic approach to the synthesis of sialoglycoconjugates containing an α-sialyl-(2→8)-α-sialyl-(2→8)-sialic acid unit α-glycosidically linked to O-3 of a galactose residue in their oligosaccharide chains. Glycosylation of 2-(trimethylsilyl)ethyl 6-O-benzoyl-β-d-galactopyranoside (4) or 2-(trimethylsilyl)ethyl 2,3,6,2′,6′-penta-O-benzyl-β-lactoside (5), with methyl [phenyl 5-acetamido-8-O-[5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1”, 9′-lactone)-4,7-di-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1′, 9-lactone]-4,7-di-O-acetyl-3,5-dideoxy-2-thio-d-glycero-d-galacto-2-nonulopyranosid]onate (3), using N-iodosuccinimide-trifluoromethanesulfonic acid as a promoter, gave the corresponding α-glycosides 6 and 8, respectively. The glycosyl donor 3 was prepared from trimeric sialic acid by treatment with Amberlite IR-120 (H+) resin in...

A synthetic approach to polysialogangliosides containing α-sialyl-(2 → 8)-sialic acid: total synthesis of ganglioside GD 3

A stereocontrolled, facile total synthesis of ganglioside GD 3 is described as an example of a proposed systematic approach to the preparation of gangliosides containing an α-sialyl-(2 → 8)-sialic acid unit α-glycosidically linked to O-3 of a d-galactose reesidue in their oligosaccharide chains. Glycosylation of 2-(trimethylsilyl)ethyl 6- O-benzoyl-, 3- O-benzoyl-, or 3- O-benzyl-β- d-galactopyranosides, or 2-(trimethylsilyl)ethyl 2,3,6,2′,6′-penta- O-benzyl-β-lactoside ( 7), with methyl [phenyl 5-acetamido-8- O-(5-acetamido-4,7,8,9- tetra- O-acetyl-3,5-dideoxy- d- glycero-α- d- galacto-2-nonulopyranosyl-ono-1′,9-lactone)-4,7-di- O-acetyl-3,5-dideoxy-2-thio- d- glycero- d- galacto-2-nonulopyranosid]onate ( 3), using N-iodosuccinimide-trifluoromethanesulfonic acid as a promoter, gave the corresponding α glycosides 8 (32%), 13 (33%), 14 (48%), and 17 (31%), respectively. The glycyl donor 3 was prepared from O-(5-acetamido-3,5-dideoxy- d- glycero-α- d-galacto-2-nonulopyranosylonic acid)-(2 → 8)-5-acetamido-3,5-dideoxy- d- glycero- d- galacto-2-nonulopyranosonic acid by treatment with Amberlite IR-120 (H +) in methanol, O-acetylation, and subsequent replacement of the anomeric acetoxy group with phenylthio. Compound 8 was converted into the methyl β-thioglycoside via O-benzoylation, replacement of the 2-(trimethylsilyl)ethyl group by acetyl, and introduction of the methylthio group by reaction with methylthiotrimethylsilane. Compound 17 was converted, via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and reaction with trichloroacetonitrile, into the α-trichloroacetimidate, which was coupled with (2S,3R,4E)-2-azido-3 O-benzoyl-4-octadecene-1,3-diol to give the β-glycoside. This glycoside was easily transformed, via selective reduction of the azido group, condensation with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester and lactone functions, into ganglioside GD 3.

The action of Trypanosoma cruzi trans-sialidase on glycolipids and glycoproteins.

Addition of sialic acid residues in the human pathogen Trypanosoma cruzi glycoconjugates is mediated by a trans-sialidase and not by a CMP-sialic acid:glycoconjugate sialyltransferase. Incubation of trans-sialidase with N-[galactose-14C]acetyllactosamine and O-linked oligosaccharides, N-linked glycopeptides (both obtained from fetuin) or sialyllactose showed that the last three compounds were donors of sialic acid residues to the first one. Moreover, N- and O-linked oligosaccharides in asialofetuin and asialomucin, respectively, served as acceptors of sialic acid units. Gangliosides GM3, GD1a and GT1b but not GM2, GM1a nor GD1b donated sialic acid units to N-acetyllactos amine when incubated with trans-sialidase. This showed that only sialic acid units bound to terminal galactosyl residues were transferred. GM1a was converted to GD1a, and GD1b to GT1b when incubated with the appropriate donor. The fact that asialo-GM1a was converted to a ganglioside migrating as GD1a on thin-layer chromatography suggested that sialic acid units may be transferred to internal galactosyl residues, although once linked to those residues they can not be further transferred to other glycoconjugates. Sialic acid residues linked alpha 2,3- but not alpha 2,6- or alpha 2,8- were transferred by the trans-sialidase. Methyl beta-galactoside but not methyl alpha-galactoside served as acceptor of sialic acid units, thus suggesting that terminal alpha-linked galactosyl units in T. cruzi and mammalian glycoproteins are not sialylated by the enzyme. As the trans-sialidase employed in these experiments has been shown to be located on the external surface of the parasite and to be shed to the medium, the relatively broad specificity shown by the enzyme with respect to protein- and lipid-linked oligosaccharides strongly suggests that infection by T. cruzi might alter the sialic acid distribution in glycoproteins and glycolipids of the mammalian host.

N-glycosylation in trypanosomatid protozoa.

Trypanosomatid protozoa are parasites of considerable medical and economic importance in developing countries. The pathway leading to N-glycosylation in these microorganisms is characterized by the following features: (i) dolichols are composed of only 10-13 isoprene units; (ii) oligosaccharides transferred in N-glycosylation have the compositions Man(6,7,9)GlcNAc2, depending on the species; (iii) trypanosomatids are unable to synthesize dolichol-P-Glc and, in addition, some species lack certain dolichol-P-Man-dependent mannosyltransferases; (iv) the oligosaccharyltransferase does not require the presence of glucose units in the oligosaccharide in order to catalyse an efficient transfer reaction; (v) trypanosomatids have a glucosidase II-like enzyme, but lack glucosidase I; (vi) glucosidase II is required for deglucosylation of oligosaccharides glucosylated by the UDP-Glc:glycoprotein glucosyltransferase, an activity first detected in those parasites; (vii) the structures of polymannose-type compounds in these protozoa have no significant differences with those of their mammalian counterparts except for the presence, in certain species, of oligosaccharides having galactofuranose units linked to external mannose residues; (viii) biantennary complex-type oligosaccharides having in some cases terminal alpha-linked galactose units or poly-N-acetylactosamine extensions, but lacking sialic acid units, have been described in Trypanosoma brucei; (ix) complex-type oligosaccharides having alpha-linked galactose, fucose and sialic acid residues have been described in Trypanosoma cruzi. In this parasite, addition of sialic acid units to glycoproteins and glycolipids is mediated by a trans-sialidase located on the external surface of the parasite and not by an intracellular CMP-sialic acid-dependent sialyltransferase.

Preparation of lyso-GM1 (II3Neu5AcGgOse4-long chain bases) by a one-pot reaction.

A simple procedure is described for preparing lyso-GM1, a GM1 derivative that lacks the fatty acid moiety, starting from GM1 ganglioside using a one-pot reaction. Ganglioside deacylation was carried out in KOH/propan-1-ol in the absence of oxygen. The yield of lyso-GM1 under optimal conditions (6 h, 90 degrees C, 0.2 N KOH, 1 mM GM1) was 54%. The chemical structure of lyso-GM1 was determined by 1H-NMR and FAB-MS analyses, thus proving that the acetamide groups of galactosamine and sialic acid units were not affected during the deacylation reaction.

Identification of the gene(s) coding for the trans-sialidase of Trypanosoma cruzi.

The gene(s) encoding the Trypanosoma cruzi shed-acute-phase-antigen (SAPA) has a 5' end encoding a region containing two totally and two partially conserved Ser-X-Asp-X-Gly-X-Thr-Trp motifs which are present in bacterial neuraminidases, and a 3' end encoding tandemly repeated units of 12 amino acids. It is now reported that 54-87% of the total neuraminidase activity present in the parasite could be immunoprecipitated with polyclonal or monoclonal antibodies against the repeated amino acid units of SAPA. These immunoprecipitates also had greater than 80% of the trans-sialidase activity of the parasite. SAPA used sialyllactose, fetuin and 4-methylumbelliferyl-sialic acid as substrate donors. In the presence of a suitable acceptor molecule (lactose) the sialic acid residues were transferred to the disaccharide, whereas in the absence of acceptors the residues were transferred to water. If relatively inefficient acceptors (maltose or cellobiose) were added to the incubation mixtures, the sialic acid units were transferred both to the disaccharides and to water. It is concluded that a major T. cruzi antigen has both the trans-sialidase and the neuraminidase activities of the parasite. Both activities are probably located on the N-terminus of SAPA since antibodies directed against the C-terminus, which contains the repeated amino acid units, do not affect the enzymatic activities.

N-Acetyllactosaminooligosaccharides that contain the β- d-Glc pNAc-(1→6)- d-Gal or β- d-Glc pNAc-(1→6)- d-GalNAc sequences reveal reduction-sensitive affinites for wheat germ agglutinin

Affinity chromatography of unreduced oligosaccharides on a small column of immobilized wheat germ agglutinin (WGA) revealed high-binding affinites for several radiolabeled molecules containing at the reducing end either β- d-Glc pNAc-((1→6)- d-Glc p-(1→6)-β- d-Gal p-(1→4)- d-GlcNAc, β- d-Glc pNAc-(1→6)- β- d-Gal p(1→4) dGlc, d-Glc pNac-(→3)-[β- d-Glc pNAc-(1→6)- d-GalNAc, or β- d-Gal p-(→3)-[β- d-Glc pNAc-(1→6)- d-GalNAc sequences. Reduction changed the binding affinites remarkably: The sequences carrying a d-galactose or 2-acetamido-2-deoxy- d-galactose residue at the reducing end lost most of their affinities, but the sequences containing a d-glucose or 2-acetamido-2-deoxy- d-glucose residue at the reducing end gained additional affinity upon reduction. These findings emphasize the role of the unreduced, 6-o-substituted d-galactose and 2-acetamido-2-deoxy- d-galactose residues for the binding of saccharides to WGA, which has been recognized previously as a lectin specific for oligosaccharides containing a 2-acetamido-2-deoxy- d-glucose or sialic acid unit. The results suggested also that WGA-agarose chromatography of alditols may become a valuable method for the fractionation of oligo- N-acetyllactosaminoglycans and related saccharides.

Synthesis, structure, and conformation of the dilactone derivative of Gd1b ganglioside

Treatment of GD1b, β-Gal-(1→3)-β-GalNAc-(1→4)-[α-Neu5Ac-(2→8)-α-Neu5Ac-(2→3)]-β-Gal-(1→4)-β-Glc-(1→1)-Cer, with dicyclohexylcarbodi-imide in anhydrous methyl sulfoxide affords 95–98% of GD1b-dilactone. The carboxyl groups of the two sialic acid units are involved in ester linkages, as proved by ammoniolysis and reduction which gave derivatives containing the amide of sialic acid and N-acetylneuraminulose, respectively. 1H-N.m.r. spectroscopy showed that the lactone rings involved position 9 of the inner sialic acid and position 2 of the inner galactose and that the disialosyl chain is extended toward the -β-Gal-(1→4)-β-Glc- portion of the ganglioside moiety.

Common cleavage pattern of polysialic acid by bacteriophage endosialidases of different properties and origins.

The cleavage specificities of seven bacteriophage endosialidases degrading the alpha 2-8-linked polysialic acid common to bacterial polysaccharides and to the cell adhesion molecule N-CAM were investigated. The bacteriophages studied represented five different phenotypic groups by protein and DNA fragment analysis and two different morphology groups by electron microscopy. Characterization of the fragments arising from the native or chemically modified substrates of different sizes showed that cleavage specificity was influenced by enzyme concentration. At the initial phase of degradation, at concentrations ranging from 20- to 100-fold, the minimum substrate size was an oligomer of eight (in one case, nine) sialic acid units that was preferably cleaved at the same position. Under exhaustive conditions, the oligomers were degraded further, and each enzyme type had its own specificity. The similar initial cleavage of polysialic acid by endosialidases associated with phages of different properties and morphology suggests a conserved mechanism of enzyme-substrate interaction. This mechanism may be conformationally determined and related to the specific properties of polysialic acid in other molecular interactions.

Reexpression of poly(sialic acid) units of the neural cell adhesion molecule in Wilms tumor.

A unique structural feature of the neural cell adhesion molecule N-CAM is the presence of homopolymers of alpha (2----8)-linked sialic acid units. We have used two specific probes for the detection of poly(sialic acid) in normal human kidney and Wilms tumor: a monoclonal antibody against meningococci group B capsular polysaccharide (homopolymers of alpha (2----8)-linked sialic acid units), which shows no crossreactivity with polynucleotides and denaturated DNA, and bacteriophage-induced endosialidases specifically hydrolyzing alpha (2----8)-linked poly(sialic acid) units. Additionally, for the detection of N-CAM, antibodies recognizing the polypeptide portion of the molecule and biotinylated antisense RNA transcribed from a cDNA clone for N-CAM were applied. Poly(sialic acid) was regionally detectable in human embryonic kidney but undetectable in normal adult kidney, as already reported for rat kidney. The malignant Wilms tumor, which is characterized by the presence of structural components resembling those found in embryonic kidney, reexpressed poly(sialic acid) units and showed positive immunostaining for the polypeptide portion of N-CAM. Immunoblot analysis of Wilms tumor as well as human embryonic kidney and brain with the monoclonal anti-poly(sialic acid) antibody revealed in each case the same high molecular mass broad band. In situ hybridization demonstrated the presence of mRNA for N-CAM in Wilms tumor. We conclude that poly(sialic acid), most probably present on N-CAM, is an oncodevelopmental antigen in human kidney.

Ganglioside lactones:1H-NMR determination of the inner ester position of GD1b-ganglioside lactone naturally occurring in human brain or produced by chemical synthesis

The complete definition of the chemical structure of GD1b-ganglioside (GD1b) lactone isolated from human brain has been given by means of spectrometric and spectroscopic analyses. GD1h lactone contains a single ester linkage involving the external sialic acid carboxyl group and the C-9 hydroxyl group of the internal sialic acid unit. A synthetic lactone of GD1b prepared treating GD1b with glacial acetic acid characterized in the same way showed an identical chemical structure.

Metabolism and function of gangliosides in developing neurons.

Previous experiments have shown that the addition of a mixture of gangliosides to the growth medium induced morphological changes in primary neuronal cultures, producing especially a trophic effect and a sprouting of neurites (neuritogenesis). The study reported here examined the changes of some biochemical parameters that paralleled the morphological modifications of cultured neurons from chick brain hemispheres treated with gangliosides. Neurons cultured from 3 to 7 days in the presence of various concentrations of a purified mixture or of single-species of gangliosides (GM1, GD1a, GT1b) revealed that these glycolipids were easily incorporated into the cells as a function of their exogenous concentrations. Incubation of neurons with N-acetyl-D-[U-14C]mannosamine showed a final labeling of all endogenous cellular and exogenous incorporated gangliosides; however, the radioactivity recovered decreased as a function of the number of sialic acid units of the exogenously added gangliosides. The treatment of neuronal cells from 3 to 7 days in culture with a mixture of 10(-8) M and 10(-5) M gangliosides led to the following observations on some neurochemical parameters: no effect on the influx of choline and dopamine; no effect on the spontaneous choline efflux, whereas the K+-provoked one is abolished; decrease of the spontaneous and K+-stimulated release of dopamine; no effect on the spontaneous release of GABA for 10(-8) M gangliosides but an increase of both spontaneous and K+-provoked release for 10(-5) M gangliosides. The data suggest that the possible insertion of gangliosides into the neuronal membranes may imply structural modifications that may influence enzymatic activities, neurotransmitter transport, and finally, some nerve cell mechanisms.

Demonstration of a natural antigalactosyl IgG antibody on thalassemic red blood cells

A modified antiglobulin test, based on the high affinity between the Fc portion of the red blood cell (RBC) bound IgG and the Fc receptor on the myeloid cell K-562, was utilized for demonstration of immunoglobulins (Ig) on thalassemic RBC. Ig was found on the RBC of 73 out of 80 patients with thalassemia. The immunoglobulins on the thalassemic RBC belonged to the IgG subclass and were autoreactive. Elution studies utilizing various carbohydrates, or by thermal stripping, indicated that at least part of the IgG molecules found on the thalassemic RBC were specifically reactive with terminal galactosyl residues on the RBC membrane. IgG antibodies with similar reactivity were also demonstrated in normal human serum. These natural antigalactosyl IgG antibodies from normal sera could bind to IgG- depleted thalassemic RBC. Thalassemic RBC and normal senescent RBC were previously found to contain reduced amounts of membrane sialic acid (SA). It is suggested that the antigalactosyl IgG antibodies interact with newly exposed galactosyl residues underlying the sialic acid units. Such interaction may lead to the shortened lifespan of thalassemic RBC and may result in sequestration of senescent normal RBC by the reticuloendothelial system.

Demonstration of a Natural Antigalactosyl IgG Antibody on Thalassemic Red Blood Cells

A modified antiglobulin test, based on the high affinity between the Fc portion of the red blood cell (RBC) bound IgG and the Fc receptor on the myeloid cell K-562, was utilized for demonstration of immunoglobulins (Ig) on thalassemic RBC. Ig was found on the RBC of 73 out of 80 patients with thalassemia. The immunoglobulins on the thalassemic RBC belonged to the IgG subclass and were autoreactive. Elution studies utilizing various carbohydrates, or by thermal stripping, indicated that at least part of the IgG molecules found on the thalassemic RBC were specifically reactive with terminal galactosyl residues on the RBC membrane. IgG antibodies with similar reactivity were also demonstrated in normal human serum. These natural antigalactosyl IgG antibodies from normal sera could bind to IgG-depleted thalassemic RBC. Thalassemic RBC and normal senescent RBC were previously found to contain reduced amounts of membrane sialic acid (SA). It is suggested that the antigalactosyl IgG antibodies interact with newly exposed galactosyl residues underlying the sialic acid units. Such interaction may lead to the shortened lifespan of thalassemic RBC and may result in sequestration of senescent normal RBC by the reticuloendothelial system.

Structural studies on the sialic acid polysaccharide antigen of Escherichia coli strain Bos-12

A polysaccharide, antigenically related to group C meningococcus, has been isolated from Escherichia coli strain Bos-12 (016; K92; NM). Like groups B and C meningococcal polysaccharide, the Bos-12 antigen is a pure polymer of sialic acid. 13C NMR studies on the meningococcal group B and C polysaccharides have indicated that the former consists of sialic acid units linked 2 leads to 8- alpha, whereas the latter contains the sialic acid residues linked 2 leads to 9-alpha (Bhattacharjee, A.K., Jennings, H.J., Kenny, C.P., Martin, A., and Smith, I.C.P. (1975), J. Biol. Chem. 250, 1926). Comparison of natural abundance 13C NMR spectra of the Bos-12 polysaccharide with group B and C meningococcal polysaccharides established that Bos-12 was either (a) an equimolar mixture of 2 leads to 8-alpha linked sialic acid homopolymers or (b) a 2 leads to 8-alpha/2 leads to 9-alpha heteropolymer. These possibilities were distinguished in the following manner. The fact that Bos-12 polysaccharide precipitated with anti-group C serum but not with anti-group B serum would seem to exclude a. Further, chemical studies (periodate oxidation followed by tritiated NaBH4 reduction) gave saccharides with a radioactive-labeling pattern expected for alternating 2 leads to 8-alpha/2 leads to 9-alpha sialic acid linkages. Bos-12 is thus an 2 leads to 8/2 lead to 9-alpha heteropolymer.

Stimulation of chick retinal ganglioside synthesis by light

Ganglioside biosynthesis in chick retina during light- and dark-adaptation was investigated. This study was performed in vivo in 9-day-old chicks by intravitreal injection of N-acetyl[ d-mannosamine U- 14C], the most specific precursor of sialic acid. Chicks were then either light- or dark-adapted. In both cases, all retinal gangliosides because rapidly labelled. The activities, expressed in cpm/μg of N-acetyl-neuraminic acid (NeuNAc), or total [ 14C]ganglioside were higher for the light-aapted animals. Differences between the activities were important during the first 18 hours after injection of the NeuNAc precursor. Maximum activity occurred between 1 and 6 days, after this period both activities were similar. Light stimulation of ganglioside NeuNAc was also observed for individual gangliosides, especially for the monosialoganglioside G M3 and the disialogangliosides G D3, G D1b and G D1a. These gangliosides had the highest activity. The activity of retinal G M1 was lower or equal to that of the polysialogangliosides for light- as well as for dark-adapted animals. The results lead us to assume that the other sialic acid units incorporated into the monosialoganglioside G M1 to form polysialogangliosides were furnished by different NeuNAc pools.

The Specific Hapten of Group C (Group II α) Meningococcus

Summary The specific hapten of Group C (formerly Group II α) meningococcus appears to be predominantly a polymer of a sialic acid congener, as evidenced by its nearly complete conversion to humin-like material on aqueous acid hydrolysis, specific colorimetric analyses, infrared absorption spectrum, periodate oxidation, quantitative elementary and group analyses, correlation of sialic acid content with serologic activity, and conversion by hydrolysis in methanolic hydrochloric acid into products having characteristics of a sialic acid. Hexosamine determinations and nitrogen content indicate that this polymer contains hexosamine units as well as sialic acid units.