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ABSTRACT: The structure of the O-specific side chain of the lipopolysaccharide from the Gram-negative psychrophilic bacterium Moritella viscosa strain M2-226, responsible for the winter ulcer in Atlantic salmon, has been determined. Monosaccharide analysis and (1)H and (13)C NMR spectroscopy were employed to elucidate the structure. It was concluded that the polysaccharide is composed of a trisaccharide repeating unit with the following structure: →3)-β-D-GlcpNAc-(1→4)-[α-D-GlcpA-(1→3)]-α-L-Fucp-(1→ .
Carbohydrate research 10/2011; 347(1):164-7. · 2.03 Impact Factor
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ABSTRACT: Immunochemical analysis of the Yokenella regensburgei lipopolysaccharides (LPS) indicated the presence of the core oligosaccharide-related immunotypes among the investigated strains. The structure of the core oligosaccharide segment of the Y. regensburgei LPS has been investigated using chemical methods, mass spectrometry, and (1)H, (13)C NMR spectroscopy. It was concluded that the core oligosaccharides of the strains PCM 2476 and PCM 2477 are composed of an undecasaccharide. The combined data revealed two immunotypes of the core oligosaccharide recognized by antibodies against the whole bacterial cells. The structural differences between the core oligosaccharides are limited to the outermost terminal hexopyranose residue. In the core oligosaccharide of the strain PCM 2476, it was identified as alpha-d-Glcp and in that of the strain PCM 2477 as alpha-d-Galp. This subtle difference between the glycoforms of the LPS core appeared to be essential for formation of the epitopes recognized by the specific antibodies directed against the Y. regensburgei whole bacterial cells. The oligosaccharides are not substituted by phosphate groups. Instead, the carboxyl groups of Kdo and galacturonic acid residues present in the core provide the negative charges. The undecasaccharides represent a novel core type of bacterial LPS, which is characteristic for Y. regensburgei.
Glycobiology 10/2009; 20(2):207-14. · 3.58 Impact Factor
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ABSTRACT: Many sessile suspension-feeding marine organisms rely on chemical defense to keep their surfaces free from fouling organisms. The brominated cyclopeptides barettin (cyclo[(6-bromo-8-entryptophan)arginine]) ( 1) and 8,9-dihydrobarettin (cyclo[(6-bromotryptophan)arginine]) ( 2) from the cold-water sponge Geodia barretti have previously displayed settlement inhibition of barnacle larvae in a dose-dependent manner. In this paper, we describe a novel dibrominated cyclopeptide, bromobenzisoxazolone barettin (cyclo[(6-bromo-8-(6-bromobenzioxazol-3(1 H)-one)-8-hydroxy)tryptophan)]arginine) ( 3), which we have isolated from G. barretti and which displays settlement inhibition of barnacle larvae ( Balanus improvisus) with an EC 50 value of 15 nM. The chemical structure was determined using MS and 2D-NMR.
Journal of Natural Products 04/2008; 71(3):330-3. · 3.13 Impact Factor
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ABSTRACT: In this work, we show the potent antifouling effects of two compounds, barettin (cyclo[(6-bromo-8-entryptophan)arginine]) (1), isolated as a Z/E mixture (87/13), and 8,9-dihydrobarettin (cyclo[(6-bromotryptophan)arginine]) (2), isolated from the marine sponge Geodia barretti. The compounds were isolated guided by their ability to inhibit the settlement of cyprid larvae of the barnacle Balanusimprovisus, and their structures were determined by means of mass spectrometry, NMR, and quantitative amino acid analysis. The activities of these brominated diketopiperazine-like cyclic dipeptides are in the range of antifouling agents in use today, as shown by their EC(50) values of 0.9 and 7.9 microM, respectively. However, contrary to today's antifouling agents, the effects of barettin and 8,9-dihydrobarettin are nontoxic and reversible. A small set of synthetic analogues, including l-arginine, l-tryptophan, 5-bromo-d,l-tryptophan, 6-bromo-d,l-tryptophan, and 6-fluoro-d,l-tryptophan, were tested for possible structure-activity relationships. None of these compounds showed any effect at a concentration of 10 microM. We hypothesize that the isolated compounds are part of the sponge's chemical defense to deter fouling organisms. This theory is supported by the fact that barettin is found in water exposed to living specimens of G. barretti in concentrations that completely inhibit barnacles from settling.
Journal of Natural Products 04/2004; 67(3):368-72. · 3.13 Impact Factor
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ABSTRACT: Dextranase catalyzes the hydrolysis of the alpha-1,6-glycosidic linkage in dextran polymers. The structure of dextranase, Dex49A, from Penicillium minioluteum was solved in the apo-enzyme and product-bound forms. The main domain of the enzyme is a right-handed parallel beta helix, which is connected to a beta sandwich domain at the N terminus. In the structure of the product complex, isomaltose was found to bind in a crevice on the surface of the enzyme. The glycosidic oxygen of the glucose unit in subsite +1 forms a hydrogen bond to the suggested catalytic acid, Asp395. By NMR spectroscopy the reaction course was shown to occur with net inversion at the anomeric carbon, implying a single displacement mechanism. Both Asp376 and Asp396 are suitably positioned to activate the water molecule that performs the nucleophilic attack. A new clan that links glycoside hydrolase families 28 and 49 is suggested.
Structure 10/2003; 11(9):1111-21. · 6.35 Impact Factor
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ABSTRACT: The direct acting mutagenic N 2-hydroxylated metabolite of the food mutagen 2-amino-1-methyl-6-phenylimidazo-[4, 5-b]pyridine (PhIP) does not react with DNA. Upon acetylation of the N 2-hydroxy-PhIP with acetic anhydride two products could be detected. Mass spectrometric analysis showed that both products were monoacetyl derivatives of N 2-hydroxy-PhIP. One of the products did not show any reactivity towards DNA and is probably the N -acetyl derivative of N 2-hydroxy-PhIP. The other product which is most likely to be N 2-acetoxy-PhIP reacted with DNA and 2'-deoxyguanosine but not with 2'-deoxycytidine, 2'-deoxy-adenosine or 2'-deoxythymidine. The PhIP-2'-deoxyguanosine adduct was purified and characterized by mass spectral, 1H and [13C]NMR analysis, showing that PhIP like the other cooked food mutagen 2-amino-3-memytiniidazo[4, 5- f ]quinoline, had reacted with C-8 of guanine forming N (2'-deoxy-guanosin-8-yl) - PhIP. HPLC analysis of enzymatically hydrolyzed calf thymus DNA which had been reacted with N2-acetoxy-PhIP showed one adduct which was chromato-graphically and spectroscopkally identical to N 2-(2'-deoxy-guanosin-8-yl)-PhIP. HPLC separation followed by liquid scintillation counting of hydrolyzed liver DNA from a rat dosed with [3H]PhlP showed that radioactivity coehited with the hydrolysis product of the synthetic PhIP-2-deoxyguanosine adduct, indicating that PhIP in vivo also forms an N 2-(2'-deoxyguanosin-8-yl)-PhIP adduct.
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ABSTRACT: The covalent binding of the mutagenic N 2-hydroxy metaboilte of the food mutagen 2-amino-3,4,8-trimethyl-3 H -lmldazo[4,5- f ]quinoxaline (4,8-DiMeIQx) to 2′-deoxy-nudeosides and DNA was investigated in vitro and in vivo . N 2-Hydroxy-4,8-DiMeIQx reacted to a small extent spontaneously with 2-deoxyguanosine. However, acetylatlon of N 2-hydroxy-4,8-DiMeIqx with acetic anhydride to form the N 2-acetoxy derivative prior to reaction with 2-deoxyguanosine resulted in much higher yield of adduct. N 2-Acetoxy-4,8-DiMeIQx did not form adducts with 2′-deoxy- adenosine, 2′-deoxycytldlne or 2′-deoxythymldlne. The adduct formed between the N metabolite of 4,8- DiMeIQx and 2-deoxyguanosine was analysed by mass spectrometry and NMR spectroscopy and the structure of the adduct was shown to be N 2-Acetoxy-4,8-DiMeIQx. N 2-Acetoxy-4,8-DiMeIQx. reacted with calf thymus DNA and formed a covalently bound 4,8-DiMeIQx residue, which could not be removed by repeated precipita tions or solvent extractions. The 4,8-DiMeIQx-DNA was hydrolysed enzymatically with nuclease P1/acid phosphat ase and HPLC analysis showed that 70% of the bound mutagen was recovered as N 2-Acetoxy-4,8-DiMeIQx. An additional minor adduct accounting for ∼15% of the bound mutagen showed UV spectral characteristics similar to N 2-(2′-deoxyguanosin-8-yl)-4,8-DiMeIQx and is probably an undigested oligomer. 32P-Postlabelling analysis of calf thymus DNA modilied with 4,8-DiMeIQx in vitro and liver DNA from rats dosed with 50 mg/kg 4,8-DiMeIQx showed a similar adduct pattern. In both samples N 2-(2′- deoxyguanosln-8-yl)-4,8-DiMeIQx accounted for 60–70% of the bound mutagen. Thus, these results show that 4,8-DiMeIQx similar to other heterocyclic amines form adducts with C-8 of guanine both in vitro and in vivo via Its N 2-OH metabolite.
