Altered terminal glycosylation of thyroglobulin in papillary thyroid carcinoma

Samples of thyroglobulin (Tg) were isolated from specimens of differentiated thyroid carcinoma of the papillary type and from normal adjacent glandular tissue, and the content of sialic acid was estimated. Also the in vitro incorporation of 14C-sialic acid, in the form of both CMP (cytidine 5'-monophospho-)--activated and non-activated N-acetyl-neuraminic acid, into Tg of malignant and morphologically normal thyroid. The sialic acid content of Tg preparations from papillary thyroid carcinomas varied considerably (0.27-0.92 mg/100 mg Tg). In six cancerous Tg samples the content of sialic acid was markedly lower than that in Tg from the corresponding apparently normal thyroid tissue (0.71:1.11 mg per 100 mg Tg). In addition, in comparison with the control, the incorporation of non-activated 14C-sialic acid into Tg of malignant thyroid tissue was considerably lower (-41%). However, the incorporation of CMP-activated 14C-sialic acid into cancerous Tg was greater than into Tg of morphologically unchanged tissue of the same gland (+29%). The reduced content and incorporation rate of sialic acid into Tg of differentiated thyroid carcinoma is probably the consequence of disturbances in terminal glycosylation of the Tg molecule in malignantly transformed thyroid tissue. The enhanced incorporation of CMP-sialic acid into cancerous Tg suggests that Tg sialylation in carcinoma is probably altered in the sialic acid activation phase.

Crude urinary human chorionic gonadotropin contains variant forms of HCG with low sialic acid content that exhibit an increased thyrotropic activity in CHO cells expressing the human TSH receptor

Hyperthyroidism occurs in association with pregnancy or trophoblastic tumours. This is due to the secretion of thyroid stimulators by trophoblastic cells, most likely hCG or a variant form of hCG. In the present studies we sought to identify hCG variants with enhanced thyrotropic activity contained in crude hCG extract from pregnancy urine (hCGc). Such studies seem now feasible, because highly sensitive assays employing CHO cells transfected with the recombinant human TSH receptor recently became available. Initially, we found the activity of hCGc to both inhibit the binding of 125I-bTSH to CHO-TSHr cells and to stimulate the cAMP release by the cells to be increased, compared to highly purified hCG (hCGp), which was tested in comparable immunological concentrations. We then processed hCGc on a DEAE-52 anionexchange column to separate materials of interest, termed hCGv, from hCGp. HCGv was further purified by gel chromatography, and found to be enriched in terms of both, its holo-hCG immunoactivity and its TSH binding inhibiting activity, compared to hCGc where it was derived from. It also proved more potent than hCGp to bind to recombinant hTSH receptor and to stimulate adenylate cyclase activity in CHO-TSHr cells. Enzymatic desialylation was able to increase the potency of both hCGv and hCGp, and rendered the two desialylated hCG forms nearly equipotent. Isoelectric focusing and direct measurement of sialic acid contents revealed hCGv to be less sialylated than hCGp.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesion and junction molecules in embryonic and adult lens cell differentiation

The expression of the neural cell adhesion molecule NCAM and its polysialic acid (PSA) moiety was documented during embryonic development and adult differentiation of chicken lens cells. In both the embryo and adult, NCAM is predominantly found in the epithelium and the zone of young elongating cells of the annular pad. NCAM abundance drops markedly in the cortical fibers and is further reduced in the lens nucleus. Epithelial cell NCAM is more highly poly-sialylated in the adult than in the embryonic lens. Three isoforms of NCAM at 180, 140, and 120 kDa were detected in the lens and predominantly associated with the unit membrane-enriched plasma membranes of fiber cells. The distribution of NCAM relative to MP26 and the adherence junction-associated glycoprotein N-cadherin suggests that NCAM could influence the formation of fiber cell gap junctions and adherence junctions.

Nature of the heterogeneity within genetic variants of bovine serum transferrin

A comparison is made of the four main components of an homozygous variant (A or D2D2) of bovine serum transferrin. These are designated I-IV in order of increasing mobility in electrophoresis at pH 7.5. Components I, II, III and IV have 2,2,3 and 3 residues of sialic acid per transferrin molecule and appear to correspond to components 2a, 2b, 3a and 3b respectively of Stratil & Spooner (1971). The difference between components I and II and between III and IV does not reside in sialic acid differences. On the basis of peptide maps of reduced carboxamidomethylated components, urea-starch gel electrophoresis and quantitative sequence studies, it is concluded that components II and IV have a scission in the peptide chain. By homology with the sequency of MacGillivray et al. (1977) for human serum transferrin it is suggested that the scission occurs between residues 55 and 54 from the C-terminus and this portion of the chain has a 'molecular' weight of ca. 6000. The implications are briefly discussed.

Effect of androgen on different biochemical constituents of human semen

Changes in the levels of fructose, sialic acid, ascorbic acid, cholesterol and acid and alkaline phosphatases in the semen were studied in eight azoospermic volunteers during administration of testosterone propionate over a four week period. In order of responsiveness, elevations were observed in the levels of acid phosphatase, fructose, sialic acid and alkaline phosphatase during androgen therapy. No changes were seen in the levels of cholesterol and ascorbic acid.

A simple two-step protocol for the purification of human pancreatic beta cells

AIMS/HYPOTHESIS

Isolated pure human beta cells would be helpful for a number of research purposes. However, lack of beta cell-specific surface antigens has been a major problem. We aimed to develop a simple method for human beta cell isolation based on the initial elimination of ductal cells by their expression of carbohydrate antigen 19-9 (CA19-9), followed by positive selection of beta cells by their expression of polysialic acid-neural cell adhesion molecule (PSA-NCAM).

METHODS

Cell type-specific expression of CA19-9, NCAM and PSA-NCAM was studied in sections of adult human pancreas and in cultured primary endocrine and exocrine cells. Dispersed human islet cells were purified in two steps, after 4 days of suspension culture, by binding to magnetic microbeads coupled to antibodies against CA19-9 and PSA-NCAM.

RESULTS

NCAM expression was detected in ducts and islets in the human pancreas. In contrast, PSA-NCAM immunoreactivity was detected only in islets. PSA-NCAM staining in dispersed cells revealed that the marker is expressed in all endocrine cell types, but not in duct cells. Purification of dispersed islet cells using PSA-NCAM microbeads alone did not completely eliminate contaminating duct cells. However, elimination of the duct cells by CA19-9 microbeads followed by positive sorting of the PSA-NCAM-positive cells in five consecutive islet preparations resulted in 90 to 98% pure endocrine cells, of which 89 to 97% were beta cells.

CONCLUSIONS/INTERPRETATION

We describe a simple and reproducible method for purification of viable human pancreatic beta cells devoid of exocrine acini and ducts.

Glycoproteins secreted by sublingual glands of the echidna (Tachyglossus aculeatus)

The portion of echnida sublingual glycoproteins which could be solubilized was fractionated by electrophoresis in polyacrylamide gel and by filtration on a column of Sephadex G-100. Analyses for carbohydrate and amino acid are given and are compared with those of the submaxillary mucins of cattle, dog, pig and sheep. The molar ratio of galactosamine to sialic acid was roughly 1:1 in the echidna fractions, the sialic acid was N-acetyl-neuraminic acid, and there was very little neutral sugar. Proline was relatively high in amount, and isoleucine, half-cystine, methionine, leucine, tyrosine, and phenylalanine were absent or present to a very small extent. The material was weakly antigenic in the rabbit.

The molecular components of human transferrin type C

Immunologically pure human transferrin type C (TfC) was isolated from the plasmas of 11 individual healthy donors. After conversion into the 2Fe-form, the preparations were analysed by polyacrylamide gel electrophoresis and chromatography on DEAE-cellulose. In all samples studied by either method the presence of three components, designated A, B and C, was observed. Calculations from eight chromatograms yielded the following relative proportions for the components: A:6%, B:62% and C:32%. The quantity of iron bound played no role in this chromatographic resolution. The components were immunologically identical but their sialic acid content increased inthe order of A less than B less than C. The presence of galactose as an ultimate residue of the oligosaccharide chains in TfC component A was confirmed by a biological test. This observation together with the results of earlier analyses for hexose, hexosamine and galactose in the subfractions from Behringwerke human transferrin, suggests that sialic acid is probably the only variable among TfC components A, B and C. Loss of sialic acid from component C during the isolation of TfC was excluded as an explanation for the presence of the other two components. The electrophoretic appearance of TfC samples from five patients with liver disease (chronic active hepatitis, cirrhosis or alcoholic liver) did not noticeably differ from that of TfC FROM HEALTHY PERSONS. Baboon transferrin resembles TfC with respect to sialic acid heterogeneity. This species was therefore studied to decide whether sialic acid is gradually lost from transferrin in the circulation or whether transferrin is not fully sialylated before discharge from the hepatocyte. Using DEAE-cellulose chromatography no difference was found between baboon transferrin molecules which were less than 6h old and those which had a mean age of 8.9 days. By inference it is suggested that the reason for the multiplicity of TfC is also likely to be biosynthetic.

Chemical studies on a hamster sublingual glycoprotein

A secretory glycoprotein was isolated from the hamster sublingual gland. It contains 65% carbohydrates, the remainder being protein. The principal type of sialic acid was identified as N-acetylneuraminic acid with about 1/4 of the molecules O-acetylated. The hexosamine occurs mainly as N-acetylgalactosamine; other sugars present are galactose and fucose. The carbohydrate side chains are linked to the protein core by an O-glycosyl linkage between seryl and threonyl residues and N-acetylgalactosamine. The glycoprotein has an apparent molecular weight of 330,000. The sialogly coprotein may act as a biological antifreeze. Relevant differences in the chemical composition of the secretory glycoproteins of the sublingual and submaxillary salivary glands of this species are briefly discussed.

Some observations on the carbohydrate composition of purified transferrin

Five subfractions were isolated on DEAE-cellulose from samples of a commercially available human transferrin preparation and their carbohydrate composition was analysed. Hexosamine, galactose and total hexose were determined in four subfractions and sialic acid in all five. The data obtained indicate that the excess number of electrophoretic bands observed in transferrin from this source is due to the loss of carbohydrates which only affects sialic acid and none of the other sugar types. The availability of the penultimate galactose residues as the terminal residues in the subfractions deficient in sialic acid was also confirmed by a biological test utilizing the rat liver. The reason for the gradual loss of sialic acid from transferrin is unknown. Freezing-thawing and lyophilization did not detectably affect the sialic acid content of purified transferrin. However, free sialic acid did appear in some preparations on storage. It is concluded that similar changes in the carbohydrate composition of other plasma glycoproteins before, during, or after purification can be expected to exert an adverse effect on their usefulness as metabolic tracers.

Preliminary X-ray crystallographic and physico-chemical investigations of human ceruloplasmin

Single crystals of the plasma protein ceruloplasmin (CP) and its two modified forms: neuraminidase-treated CP (asialoCP) and NaN3-inhibited CP (NaN3-CP) suitable for X-ray studies have been grown. The native CP crystallizes as described previously by Magdoff-Fairchield et al. (1969) in the tetragonal space group 14 (a = b = 268.2 A, c = 129.1 A) with two protein molecules in the asymmetric part of a unit cell. AsialoCP crystals belong to the trigonal space group P 3(1)21 or P321 (a = b = 215.0 A, c = 84.5 A) and have one protein molecule in the asymmetric part of a unit cell. NaN3-CP crystals are isomorphous to crystals of native CP. Despite some differences in electrophoretic mobility and optical properties, the conformations of the native CP molecule and its modified forms are similar, as can be concluded from a study of ORD and CD spectra.

Derivatization of sialic acids for stabilization in matrix-assisted laser desorption/ionization mass spectrometry and concomitant differentiation of alpha(2 --> 3)- and alpha(2 --> 6)-isomers

Sialylated carbohydrates usually decompose by loss of sialic acid when ionized by matrix-assisted laser desorption/ionization (MALDI) as the result of the labile carboxylic proton. Stabilization has previously been achieved by forming methyl esters with methyl iodide, a procedure that eliminates the labile proton. In this paper, we describe an alternative procedure for methyl ester formation that provides information on the sialic acid linkage directly from the MALDI spectrum. The sugars were desalted, dissolved in methanol, and treated with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). After removal of the solvent, the products were transferred directly to the MALDI target and examined from 2,5-dihydroxybenzoic acid. Small amounts of N-glycans derived from biological sources benefited from an additional clean-up stage involving Nafion 117. alpha(2 --> 6)-Linked sialic acid produced only methyl esters whereas alpha(2 --> 3)-linked sialic acids were converted into their lactones providing a 32 Da difference in mass. Negative ion collision-induced decomposition (CID) mass spectra of these neutralized glycans provided information, in many cases, on the antenna of N-linked glycans to which the variously linked sialic acids were attached. The method was applied to N-linked glycans released from bovine fetuin and porcine thyroglobulin.

Asthma induction in mice leads to appearance of alpha2-3- and alpha2-6-linked sialic acid residues in respiratory goblet-like cells

Allergic asthmatic inflammation in mice was induced by sensitization with ovalbumin and lipopolysaccharide from Escherichia coli and visualized in the airways of asthmatic mice by spatial and temporal changes of carbohydrates containing sialic acid residues. Immunohistochemistry was used to demonstrate binding of lectins and antibodies that detect alpha2-3- and alpha2-6-linked sialic acid residues. After sensitization and challenge, the histology of the lung changed markedly, and goblet-like cells appeared, most likely caused by Clara cell metaplasia. Normal Clara cells showed no reaction after incubation with the sialic acid detecting agents, while the goblet-like cells expressed both alpha2-3- and alpha2-6-linked sialic acid residues in the asthmatic animals. The lectins but not the antibodies reacted with intestinal goblet cells. Instead, an antibody recognizing a disialoganglioside, stained large mononuclear cells in the submucosa, indicating a difference in sialylation between goblet cells in the intestine and goblet-like cells developed from Clara cells.

Chemical aspects of tracheal glycoproteins

The chemical characteristics of tracheal mucus obtained directly from the epithelial surface of the trachea indicate that the mucus from each animal source consists of a group of sulphated sialic acid-containing glycoproteins. Fractionation of the native glycoprotein from the cat by gel chromatography in the presence of urea and dithiothreitol suggests a value of about 3 X 10(6) for the molecular weights. The chief monosaccharide constituents are N-acetylneuraminic acid, N-acetylglucosamine, N-acetylgalactosamine, fucose and galactose. In the goose tracheal mucin, mannose is present (serum proteins being absent). Doubly labelled cat mucus, obtained by giving Na235SO4 and [3H]glucose simultaneously into the lumen of the trachea, is massively released by parasympathetic agents, e.g. pilocarpine. The resulting mucus has a high content of 35S and is derived largely from submucosal gland cells. Subsequent exposure to an irritant, ammonia, releases a low sulphation fraction, highly labelled with 3H, arising from goblet cells. Evidence supports the view that the overall mucus is composed of mixed secretions, chemically distinct, from different cellular synthesizing sites. Differential nervous stimulation of the various sites may cause far-reaching changes in the chemical and physical properties of the mucus by selective action on the secretion of one or more of the contributing glycoproteins.

Development of sensitive chemical and immunochemical methods for detecting sulfated sialic acids and their application to glycoconjugates from sea urchin sperm and eggs

Sulfated sialic acid (SiaS) is a unique sialic acid (Sia) derivative in which an additional anionic group is attached to a carboxylated monosaccharide. Very little is known about the occurrence and biologic function of SiaS, due to the limitations of analytical methods to detect it in minute amounts. In this study, to develop methods and probes for detecting and pursuing the functions of SiaS, we developed sensitive chemical and immunochemical detection methods. First, we synthesized as model compounds 4-methylumbelliferyl glycosides of 8-O- and 9-O-sulfated Sia consisting of N-acetylneuraminic acid (Neu5Ac), N-glycolylneuraminic acid (Neu5Gc), and deaminoneuraminic acid (Kdn). Second, we applied fluorometric high performance liquid chromatography (HPLC) analysis to these synthetic glycosides. After acid hydrolysis of the samples, the liberated SiaS were labeled with a fluorescent reagent, 1,2-diamino-4,5-methylenedioxybenzene, and analyzed on fluorometric HPLC. We established an optimal elution condition for successful separation of 8-O- and 9-O-sulfated Neu5Ac, Neu5Gc, and Kdn on HPLC. Third, we generated a monoclonal antibody (mAb) 2C4 against SiaS using sea urchin egg components as the immunogen. mAb.2C4 recognizes both 8-O-sulfated Neu5Ac (Neu5Ac8S) and Neu5Gc8S, whereas the previously prepared mAb.3G9 only recognizes Neu5Ac8S. Finally, using the fluorometric HPLC and monoclonal antibodies, we demonstrated that glycoconjugates from sea urchin sperm exclusively contained Neu5Ac8S, whereas those from eggs contained Neu5Gc8S. Furthermore, we clarified the quantitative differences in the SiaS content in eggs and sperm from two different species of sea urchins. Immunostaining using mAb.2C4 showed that Neu5Gc8S is localized in the cortical granules in unfertilized eggs, whereas it is localized in the outer surface of the fertilization layer as well as in the inner surface of fertilized eggs. Thus, 8-O-sulfation is dependent on the species, gametic cell-type, site-localization of the eggs, and glycoconjugates.

Thyroid gangliosides with high affinity for thyrotropin: potential role in thyroid regulation

Thyroid cell membranes contain a multiplicity of gangliosides, some of which inhibit thyrotropin binding to thyroid membranes. The most potent inhibitor is a ganglioside which is present in only trace amounts and appears to have a novel structure. Thyroid gangliosides may play a role in relaying the hormonal message to the thyroid cell.

Erythrocyte surface sialic acid levels of clinically healthy mongrel and exotic (alsatian and terrier) breeds of dogs

The erythrocyte surface sialic acid concentration of clinically healthy mongrel and exotic (Alsatian i.e. German shepherd and Terrier) breeds of dogs was analyzed in order to determine their role in the genetic resistance of these breeds of dogs to diseases that cause anaemia. The mean erythrocyte surface sialic acid (ESA) concentration was 57.08 +/- 1.67, 34.50 +/- 2.30 and 20.20 +/- 3.54 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier breeds of dogs, respectively, on acid hydrolysis. The mean values of ESA obtained following enzymic hydrolysis of haemoglobin-free erythrocyte membranes using Clostridium chauvoei (Jakari strain) sialidase were 49.08 +/- 0.41, 30.97 +/- 1.82 and 18.64 +/- 0.75 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier dogs respectively. When Trypanosoma vivax sialidase was used the ESA values obtained were 50.81 +/- 0.37, 41.70 +/- 0.94 and 19.65 + 0.65 mg/dl for Mongrel, Alsatian (German shepherd) and Terrier breeds of dogs respectively. This represents a statistically significant difference (P < 0.001) between the mean ESA concentration of all the breeds of dogs investigated in this study. The higher mean ESA concentration in Mongrel dogs, compared to the exotic breeds may be responsible for their resistance to disease conditions, whose aetiologic agents produce neuraminidase and also cause anaemia.

Derivatization for stabilizing sialic acids in MALDI-MS

While matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is useful in oligosaccharide analysis, the sialic acid, or N-acetylneuraminic acid (NANA), moiety of an oligosaccharide is liable to dissociation in- or postsource during mass measurement. In this study, we tried to stabilize the moiety by amidation, as in the case of peptides (Sekiya, S.; Wada, Y. Tanaka, K. Anal. Chem. 2004, 76, 5894-5902), and found 4-(4,6-dimethoxy-1,3,5-triazin-2yl)-4-methylmorpholinium chloride to be a desirable condensing agent. Amidation stabilized the glycosidic bond with NANA and suppressed its preferential cleavage by in-source decay, postsource decay, or collision-induced dissociation. In addition, the suppressed dissociation considerably improved the yield of the B/Y type ions for structural analysis by MS/MS. These results demonstrate that amidation is an effective derivatization to reinforce the structural analysis of sialylated oligosaccharides by MALDI-MS. In addition, amidation with (15)N-labeled ammonium chloride decreases the mass shift from the acid to amide form to just 0.013, reducing the complexity of mass spectral interpretation and database searching.

Reduced diversity of the human erythrocyte membrane sialic acids in polycythemia vera. Absence of N-glycolylneuraminic acid and characterisation of N-acetylneuraminic acid 1,7 lactone

Sialic acids from the erythrocyte (RBC) membrane of a patient suffering from polycythemia vera, a malignant orphan disorder of hematopoietic cells, was studied using GC/MS. We found that the sialic acid diversity of these membranes was drastically reduced since only four entities were identified: Neu5Ac (91.5%) and its 1,7 lactone Neu5Ac1,7L (7.5%) which is absent in normal RBC, Neu4,5Ac(2) (0.50%) and Neu4,5Ac(2) 9Lt (0.50%); in normal RBC, Neu5,7Ac(2), Neu5,9Ac(2), Neu5Ac9Lt, Neu5Ac8S and Neu, as well as traces of Kdn, were also present. Neu5Gc and its O-alkylated or O-acetylated derivatives, which are considered by various authors as cancer markers, were not detected.

Alpha2,6-linked sialic acid acts as a receptor for Feline calicivirus

Feline calicivirus (FCV) is a major causative agent of respiratory disease in cats. It is also one of the few cultivatable members of the family Caliciviridae. It has recently been reported that FCV binding is in part due to interaction with junction adhesion molecule-A. This report describes the characterization of additional receptor components for FCV. Chemical treatment of cells with sodium periodate showed that FCV recognized carbohydrate moieties on the surface of permissive cells. Enzymic treatment with Vibrio cholerae neuraminidase demonstrated that sialic acid was a major determinant of virus binding. Further characterization using linkage-specific lectins from Maackia amurensis and Sambucus nigra revealed that FCV recognized sialic acid with an alpha2,6 linkage. Using various proteases and metabolic inhibitors, it was shown that alpha2,6-linked sialic acid recognized by FCV is present on an N-linked glycoprotein.

Human neuroblasts migrate to the olfactory bulb via a lateral ventricular extension

The rostral migratory stream (RMS) is the main pathway by which newly born subventricular zone cells reach the olfactory bulb (OB) in rodents. However, the RMS in the adult human brain has been elusive. We demonstrate the presence of a human RMS, which is unexpectedly organized around a lateral ventricular extension reaching the OB, and illustrate the neuroblasts in it. The RMS ensheathing the lateral olfactory ventricular extension, as seen by magnetic resonance imaging, cell-specific markers, and electron microscopy, contains progenitor cells with migratory characteristics and cells that incorporate 5-bromo-2'-deoxyuridine and become mature neurons in the OB.

Structural analysis of naturally occurring sialic acids

Over the years several methodologies have been developed for the structural analysis of naturally occurring sialic acids (Sias), a family with more than 62 members. Currently there are two primary instrumental approaches: analysis of volatile Sia derivatives by gas-liquid chromatography (GLC) combined with electron-impact mass spectrometry (EI/MS), and analysis of fluorescently labeled Sias by high-performance liquid chromatography (HPLC) eventually coupled with electrospray mass spectrometry (ESI/MS). This chapter presents both approaches in detail. The volatile Sia derivatives are comprised of trimethylsilylated methyl ester derivatives, heptafluorobutylated methyl ester derivatives, or pertrimethylsilylated derivatives. The fluorescent Sia derivatives are prepared by reaction with 1,2-diamino-4,5-methylenedioxybenzene. For the identification of the different Sia derivatives, detailed GLC, HPLC, EI/MS, and ESI/MS data are included.

Diversity in cell surface sialic acid presentations: implications for biology and disease

Sialic acids (Sias) are typically found as terminal monosaccharides attached to cell surface glycoconjugates. They play many important roles in many physiological and pathological processes, including microbe binding that leads to infections, regulation of the immune response, the progression and spread of human malignancies and in certain aspects of human evolution. This review will provide some examples of these diverse roles of Sias and briefly address immunohistochemical approaches to their detection.

Structure of the O-antigen of Providencia stuartii O20, a new polysaccharide containing 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-d-galacto-non-2-ulosonic acid

The O-polysaccharide chain of the lipopolysaccharide (LPS) of Providencia stuartii O20 was found to contain d-glucuronic acid, N-acetyl-d-glucosamine, and a rarely occurring higher sugar 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-d-galacto-non-2-ulosonic acid (di-N-acetyl-8-epilegionaminic acid, 8eLeg5Ac7Ac). Degradation of the LPS with dilute acetic acid caused depolymerization of the polysaccharide chain by the ketosidic linkage to give a tetrasaccharide corresponding to the repeating unit of the polysaccharide. Based on sugar and methylation analyses of the tetrasaccharide and O-deacylated LPS as well as ESIMS, (1)H and (13)C NMR spectroscopy data, the structure of the O-polysaccharide of P. stuartii O20 was established.