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Abstract-The neutral exopolysaccharide EPS180 produced from sucrose by the glucansucrase GTF180 enzyme from Lactobacillus reuteri 180 was found to be a (1?3, 1?6)-a-D D-glucan, with no repeating units present. Based on linkage analysis, periodate oxidation, and 1D/2D 1 H and 13 C NMR spectroscopy of the intact EPS180, as well as MS and NMR analysis of oligosaccharides obtained by partial acid hydrolysis of EPS180, a composite model, that includes all identified structural features, was formulated as follows: Ó

Abstract-An NMR study of proton chemical shift patterns of known linear a-D D-glucopyranose di-and trisaccharide structures was carried out. Chemical shift patterns for (a1?2)-, (a1?3)-, (a1?4)-and (a1?6)-linked D D-glucose residues were analysed and compared to literature data. Using these data, a 1 H NMR structural-reporter-group concept was formulated to function as a tool in the structural analysis of a-D D-glucans.

The quantitative analysis by gas chromatography of monosaccharides present in glycoproteins and glycopeptides using methanolysis, followed by re-N-acetylation and trimethylsilylation, gives rise to several peaks for each monosaccharide. The identity of these peaks for xylose, fucose, mannose, galactose, glucose, N-acetylglucosamine, N-acetylgalactosamine and N-acetylneuraminic acid was established for alpha- and beta-methyl pyranosides and furanosides by combined g.l.c.-mass spectrometry and proton-magnetic-resonance spectroscopy. These data provide for the unambiguous interpretation of the gas chromatograms obtained in the application of this g.l.c. method, and supply basic information for the further application of mass spectrometry in this field.

SUMMARY Sialic acids (Sias), 9-carbon-backbone sugars, are among the most complex and versatile molecules of life. As terminal residues of glycans on proteins and lipids, Sias are key elements of glycotopes of both cellular and microbial lectins and thus act as important molecular tags in cell recognition and signaling events. Their functions in such interactions can be regulated by post-synthetic modifications, the most common of which is differential Sia-O-acetylation (O-Ac-Sias). The biology of O-Ac-Sias remains mostly unexplored, largely because of limitations associated with their specific in situ detection. Here, we show that dual-function hemagglutinin-esterase envelope proteins of nidoviruses distinguish between a variety of closely related O-Ac-Sias. By using soluble forms of hemagglutinin-esterases as lectins and sialate-O-acetylesterases, we demonstrate differential expression of distinct O-Ac-sialoglycan populations in an organ-, tissue- and cell-specific fashion. Our findings indicate that programmed Sia-O-acetylation/de-O-acetylation may be critical to key aspects of cell development, homeostasis, and/or function.

Glucosidase I is an important enzyme in N-linked glycoprotein processing, removing specifically distal alpha-1,2-linked glucose from the Glc3Man9GlcNAc2 precursor after its en bloc transfer from dolichyl diphosphate to a nascent polypeptide chain in the endoplasmic reticulum. We have identified a glucosidase I defect in a neonate with severe generalized hypotonia and dysmorphic features. The clinical course was progressive and was characterized by the occurrence of hepatomegaly, hypoventilation, feeding problems, seizures, and fatal outcome at age 74 d. The accumulation of the tetrasaccharide Glc(alpha1-2)Glc(alpha1-3)Glc(alpha1-3)Man in the patient's urine indicated a glycosylation disorder. Enzymological studies on liver tissue and cultured skin fibroblasts revealed a severe glucosidase I deficiency. The residual activity was <3% of that of controls. Glucosidase I activities in cultured skin fibroblasts from both parents were found to be 50% of those of controls. Tissues from the patient subjected to SDS-PAGE followed by immunoblotting revealed strongly decreased amounts of glucosidase I protein in the homogenate of the liver, and a less-severe decrease in cultured skin fibroblasts. Molecular studies showed that the patient was a compound heterozygote for two missense mutations in the glucosidase I gene: (1) one allele harbored a G-->C transition at nucleotide (nt) 1587, resulting in the substitution of Arg at position 486 by Thr (R486T), and (2) on the other allele a T-->C transition at nt 2085 resulted in the substitution of Phe at position 652 by Leu (F652L). The mother was heterozygous for the G-->C transition, whereas the father was heterozygous for the T-->C transition. These base changes were not seen in 100 control DNA samples. A causal relationship between the alpha-glucosidase I deficiency and the disease is postulated.

Abstract-The neutral exopolysaccharide EPS35-5 (reuteran) produced from sucrose by the glucansucrase GTFA enzyme from Lactobacillus reuteri 35-5 was found to be a (1?4, 1?6)-a-D D-glucan, with no repeating units present. Based on linkage analysis and 1D/2D 1 H and 13 C NMR spectroscopy of intact EPS35-5, as well as MS and NMR analysis of oligosaccharides obtained by partial acid hydrolysis and enzymatic hydrolysis, using pullulanase M1 (Klebsiella planticola), of EPS35-5, a composite model, that includes all identified structural elements, was formulated as follows: Ó

Helicobacter pylori NCTC 11637 produces a water‐insoluble biofilm when grown under defined conditions with a high carbon:nitrogen ratio in continuous culture and in 10% strength Brucella broth supplemented with 3 g l−1 glucose. Biofilm accumulated at the air/liquid interface of the culture. Light microscopy of frozen sections of the biofilm material showed few bacterial cells in the mass of the biofilm. The material stained with periodic acid Schiff’s reagent. Fucose, glucose, galactose, and glycero‐manno‐heptose, N‐acetylglucosamine and N‐acetylmuramic acid were identified in partially purified and in crude material, using gas chromatography and mass spectrometry. The sugar composition strongly indicates the presence of a polysaccharide as a component of the biofilm material. Antibodies (IgG) to partially purified material were found in both sero‐positive and sero‐negative individuals. Treatment of the biofilm material with periodic acid reduced or abolished immunoreactivity. Treatment with 5 mol l−1 urea at 100 °C and with phenol did not remove antigenic recognition by patient sera. The production of a water‐insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H. pylori in vivo.