Immunologically active (1-->3)-(1-->4)-alpha-D-glucan from Cetraria islandica.

A polysaccharide, Ci-3, resembling isolichenan except with a much higher degree of polymerization, has been isolated from the water extract, as well as from the alkali extract, of the lichen Cetraria islandica (L.) using ethanol fractionation, dialysis, ion-exchange chromatography and gel filtration. The mean M(r) of Ci-3 was determined to be 2000 kD, compared to 6-8 kD reported for isolichenan. The structure of Ci-3 was elucidated and found to be composed of (1-->3)- and (1-->4)-alpha-D-glucopyranosyl units in the ratio of 2:1, using methanolysis, methylation analysis, optical rotation and NMR spectroscopy. The immunomodulating activity of Ci-3 was tested in an in vitro phagocytosis assay and anti-complementary, and proved to be active in both tests.     

Identification of 3-deoxy-lyxo-2-heptulosaric acid in the core region of lipopolysaccharides from Rhizobiaceae

A 3-deoxy-2-heptulosaric acid (DHA), very probably with the lyxo-configuration, was identified in the R-core region of lipopolysaccharides from nodulating strains of Rhizobium leguminosarum, Rhizobium meliloti and from all three biovars of the phytopathogenic Agrobacterium tumefaciens. Its structure could be deduced from the fragmentation pattern of the corresponding alditol acetates obtained after reduction of the 2-keto and the 1.7-carboxy groups by sodium borohydride or sodium borodeuteride. DHA in lipopolysaccharide was not destroyed by periodate and is therefore not in a terminal position. Two DHA-containing oligosaccharides, namely glucosyl (1----4)-3-deoxy-2-heptulosaric acid and rhamnosyl-rhamnosyl-(1----5)-3-deoxy-2-heptulosaric acid could be tentatively identified by mass spectrometric methods amongst the products of mild acidic hydrolysis of lipopolysaccharides of Rhizobium leguminosarum strain 24. The two types of non-nodulating mutants of Rhizobium leguminosarum included in this study did not contain 3-deoxy-2-heptulosaric acid.     

The linkage between O-specific caryan and core region in the lipopolysaccharide of Burkholderia caryophylli is furnished by a primer monosaccharide

From the lipopolysaccharide (LPS) fraction of the plant-pathogenic bacterium Burkholderia caryophylli, the linkage between O-specific caryan and core region was characterised. The LPS fraction was first treated with 48% aqueous HF at 4 degrees C and successively with 1% acetic acid at 100 degrees C. A main oligosaccharide representing the carbohydrate backbone of the core region and a portion of the caryan (three unit of caryose) was isolated by high-performance anion-exchange chromatography. Compositional and methylation analyses, matrix-assisted laser desorption/ionisation mass spectrometry and 2D NMR spectroscopy identified the structure: [carbohydrate structure: see text]. The above residues are alpha-linked pyranose rings, if not stated otherwise. Hep is L-glycero-D-manno-heptose, Car is 4,8-cyclo-3,9-dideoxy-L-erythro-D-ido-nonose and Kdo is 3-deoxy-D-manno-oct-2-ulosonic acid. This finding indicates that QuiNAc residue is the primer monosaccharide, which connects the core oligosaccharide to caryan O-chain.     

Inhibitors of HCV NS5B polymerase. Part 1: Evaluation of the southern region of (2Z)-2-(benzoylamino)-3-(5-phenyl-2-furyl)acrylic acid

A novel series of nonnucleoside HCV NS5B polymerase inhibitors were prepared from (2Z)-2-(benzoylamino)-3-(5-phenyl-2-furyl)acrylic acid, a high throughput screening lead. SAR studies combined with structure based drug design focusing on the southern heterobiaryl region of the template led to the synthesis of several potent and orally bioavailable lead compounds. X-ray crystallography studies were also performed to understand the interaction of these inhibitors with HCV NS5B polymerase.     

Synthesis of the alpha-L-Araf-(1-->2)-beta-D-Galp-(1-->6)-beta-D-Galp-(1-->6)-[alpha-L-Araf-(1-->2)]-beta-D-Galp-(1-->6)-D-Gal hexasaccharide as a possible repeating unit of the cell-cultured exudates of Echinacea purpurea arabinogalactan.

For the characterization of the supposed epitope of an arabinogalactan, isolated from the extract of the cell-cultured Echinacea purpurea, the title hexasaccharide was synthesized. The whole synthetic route was based on the 6-O-(methoxydimethyl)methyl ether (MIP) protecting group strategy. 2-O-Benzyl-3,4-O-isopropylidene-6-O-(methoxydimethyl)methyl-beta-D-galactopyranosyl-(1-->6)-1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranose was used to prepare the desired glycosyl donor and glycosyl acceptor both carrying a persistent O-benzyl group at position 2'. Reaction of the digalactose donor and the digalactose acceptor resulted in a beta-(1-->6)-linked galactose-containing tetrasaccharide in which OH-2' and OH-2"' were substituted with benzyl groups. Hydrogenolytic removal of the benzyl groups of the tetragalactose compound gave the diol aglycon which was diarabinosylated in one step to furnish the protected target compound, whose deprotection led to the title hexasaccharide. All of the synthesized compounds were characterized by 1H and 13C NMR spectra, as well as by MALDI-TOF mass-spectrometry measurements.     

Plant members of the alpha1-->3/4-fucosyltransferase gene family encode an alpha1-->4-fucosyltransferase, potentially involved in Lewis(a) biosynthesis, and two core alpha1-->3-fucosyltransferases.

Three putative alpha1-->3/4-fucosyltransferase (alpha1-->3/4-FucT) genes have been detected in the Arabidopsis thaliana genome. The products of two of these genes have been identified in vivo as core alpha1-->3-FucTs involved in N-glycosylation. An orthologue of the third gene was isolated from a Beta vulgaris cDNA library. The encoded enzyme efficiently fucosylates Galbeta1-->3GlcNAcbeta1-->3Galbeta1-->4Glc. Analysis of the product by 400 MHz (1)H-nuclear magnetic resonance spectroscopy showed that the product is alpha1-->4-fucosylated at the N-acetylglucosamine residue. In vitro, the recombinant B. vulgaris alpha1-->4-FucT acts efficiently only on neutral type 1 chain-based glycan structures. In plants the enzyme is expected to be involved in Lewis(a) formation on N-linked glycans.     

Acetyl substitution of the O-specific polysaccharide caryophyllan from the phenol phase of Pseudomonas (Burkholderia) caryophylli

The intact O-specific caryophyllan polysaccharide of the lipopolysaccharide fraction from the bacterium Pseudomonas (Burkholderia) caryophylli was isolated for the first time. Its structure was clarified by means of chemical and spectroscopic analysis and consisted of a homopolymer of randomly acetylated caryophyllose units. The position of acetyl groups when present is not unique: all the hydroxyl-groups on the side chain of the sugar can be substituted with a slight preference for acetylation of the C-5-C-10 tail of this unusual monosaccharide     

A novel type of highly negatively charged lipooligosaccharide from Pseudomonas stutzeri OX1 possessing two 4,6-O-(1-carboxy)-ethylidene residues in the outer core region.

Pseudomonas stutzeri OXI is a Gram-negative microorganism able to grow in media containing aromatic hydrocarbons. A novel lipo-oligosaccharide from P. stutzeri OX1 was isolated and characterized. For the first time, the presence of two moieties of 4,6-O-(1-carboxy)-ethylidene residues (pyruvic acid) was identified in a core region; these two residues were found to possess different absolute configuration. The structure of the oligosaccharide backbone was determined using either alkaline or acid hydrolysis. Alkaline treatment, aimed at recovering the complete carbohydrate backbone, was carried out by mild hydrazinolysis (de-O-acylation) followed by de-N-acylation using hot KOH. The lipo-oligosaccharide was also analyzed after acid treatment, attained by mild hydrolysis with acetic acid, to obtain information on the nature of the phosphate and acyl groups. The two resulting oligosaccharides were isolated by gel permeation chromatography, and investigated by compositional and methylation analyses, by MALDI mass spectrometry, and by 1H-, 31P- and 13C-NMR spectroscopy. These experiments led to the identification of the major oligosaccharide structure representative of core region-lipid A. All sugars are D-pyranoses and alpha-linked, if not stated otherwise. Based on the structure found, the hypothesis can be advanced that pyruvate residues are used to block elongation of the oligosaccharide chain. This would lead to a less hydrophilic cellular surface, indicating an adaptive response of P. sutzeri OX1 to a hydrocarbon-containing environment.     

The structure of the core region of the lipopolysaccharide from Klebsiella pneumoniae O3. 3-deoxy-alpha-D-manno-octulosonic acid (alpha-Kdo) residue in the outer part of the core, a common structural element of Klebsiella pneumoniae O1, O2, O3, O4, O5, O8, and O12 lipopolysaccharides.

The structure of lipid A-core region of the lipopolysaccharide (LPS) from Klebsiella pneumoniae serotype O3 was determined using NMR, MS and chemical analysis of the oligosaccharides, obtained by mild acid hydrolysis, alkaline deacylation, and deamination of the LPS: [carbohydrate structure see text] where P is H or alpha-Hep; J is H or beta-GalA; R is H or P (in the deacylated oligosaccharides).Screening of the LPS from K. pneumoniae O1, O2, O4, O5, O8, and O12 using deamination showed that they also contain alpha-Hep-(1-->4)-alpha-Kdo-(2-->6)-GlcN and alpha-Kdo-(2-->6)-GlcN fragments.     

Structural analysis of a novel putative capsular polysaccharide from Pseudomonas (Burkholderia) caryophylli strain 2151.

A novel putative capsular polysaccharide consisting of D-Glcp and D-Fruf in the molar ratio of 1:1 was isolated as minor constituent from the lipopolysaccharide (LPS) fraction of Pseudomonas (Burkholderia) caryophylli. Its structure was determined, using mainly one- and two-dimensional NMR spectroscopy, as: -->6)-alpha-D-Glcp-(1-->1)-beta-D-Fruf-(2-->.     

An efficient and stereoselective synthesis of beta-D-Arap-(1-->2)-beta-D-Galp-(1-->3)-beta-D-Galp-(1-->4)-alpha-D-Manp, a tetrasaccharide fragment of Leishmania major lipophosphoglycan.

A tetrasaccharide fragment of Leishmania major lipophosphoglycan (which seems to be involved in a biological mechanism for the parasite transmission) has been synthesised using the thioglycoside, trichloroacetimidate and halide-exchange glycosylation procedures and step-wise chain elongation strategy.     

Structure of the core-oligosaccharide with a characteristic D-glycero-alpha-D-talo-oct-2-ulosylonate-(2-->4)-3-deoxy-D-manno-oct-2-ulosonate [alpha-Ko-(2-->4)-Kdo] disaccharide in the lipopolysaccharide from Burkholderia cepacia

The core oligosaccharide in the lipopolysaccharide (LPS) of Burkholderia cepacia GIFU 645(T) was investigated. After mild acid hydrolysis of the LPS, a heptasaccharide was isolated and identified by chemical analyses, GLC-MS, FABMS, and NMR spectroscopy as follows: [carbohydrate structure: see text] where L-alpha-D-Hep stands for L-glycero-alpha-D-manno-heptose, Ko for D-glycero-D-talo-oct-2-ulosonic acid, and Kdo for 3-deoxy-D-manno-oct-2-ulosonic acid.     

Photocyclization of trans-1-(1'-naphthyl)-2-(3-hydroxyphenyl)ethene: evidence for adiabatic 1trans*-->1cis* photoisomerization.

The photochemistry of trans- and cis-1-(1'-naphthyl)-2-(3-hydroxyphenyl)ethene in cyclohexane and acetonitrile was examined. In cyclohexane fluorescence is the main deactivation channel for the 1trans* isomer while photocyclization is the main reaction of the 1cis* isomer. The weighty formation of hydroxychrysene following one photon absorption by the trans isomer furnished evidence of an adiabatic 1trans*-->1cis* isomerization. The photoreactivity data in acetonitrile indicated the influence of solvent polarity on the shape of the excited state surface.     

Synthesis of 2-(4-trifluoroacetamidophenyl)ethyl O-(L-glycero-alpha-D-manno-heptopyranosyl)-(1----7)-O-(L-glycero-alpha- D-manno- heptopyranosyl)-(1----3)-L-glycero-alpha-D-manno-heptopyranoside, corresponding to the heptose region of the Salmonella Ra core structure.

The title trisaccharide was synthesized from methyl 2,3,4-tri-O-benzyl-L-glycero-alpha-D-manno-heptopyranoside by acetolysis, followed by conversion into ethyl thioglycosides and also glycosyl bromides, which were both used in glycosylation reactions. In glycosylations using thioglycosides as glycosyl donors, N-iodosuccinimide-silver triflate and dimethyl(methylthio)sulfonium triflate were used as promoters, and in glycosylations with glycosyl bromides silver triflate was used. The protecting groups introduced into intermediates during the synthesis of the title trisaccharide were designed to allow later glycosylation at O-3' to give larger oligosaccharide fragments of the Salmonella LPS core region, and also to allow the introduction of phosphate groups at O-4 and O-4', a structural element that is suggested to be present in the Ra core.     

Structure-activity relationships of novel anti-malarial agents. Part 7: N-(3-benzoyl-4-tolylacetylaminophenyl)-3-(5-aryl-2-furyl)acrylic acid amides with polar moieties

In a previous report, we have provided evidence that novel anti-malarial compounds based on 2,5-diaminobenzophenone farnesyltransferase inhibitors might benefit from the presence of a polar moiety at the para position of the terminal phenyl of the arylfurylacryloyl partial structure. Here, we demonstrate that different moieties with hydrogen bond acceptor properties lead to equipotent or even improved anti-malarial activity in comparison to the nitro group described before.     

Purification and characterization of a Neu5Ac alpha 2-->6Gal beta 1-->4GlcNAc and HSO3(-)-->6Gal beta 1-->GlcNAc specific lectin in tuberous roots of Trichosanthes japonica.

Two lectins were purified from tuberous roots of Trichosanthes japonica. The major lectin, which was named TJA-II, interacted with Fuc alpha 1-->2Gal beta/GalNAc beta 1-->groups, and the other one, which passed through a porcine stomach mucin-Sepharose 4B column, was purified by sequential chromatography on a human alpha 1-antitrypsin-Sepharose 4B column and named TJA-I. The molecular mass of TJA-I was determined to be 70 kDa by sodium dodecyl sulfate gel electrophoresis. TJA-I is a heterodimer of 38-kDa (36-kDa) and 32-kDa (30-kDa) subunits with disulfide linkage(s), and the difference between 38 and 36 kDa, and between 32 and 30 kDa, is due to secondary degradation of the carboxyl-terminal side. It was determined by equilibrium dialysis that TJA-I has four equal binding sites per molecule, and the association constant toward tritium-labeled Neu5Ac alpha 2-->6Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4GlcOT is Ka = 8.0 x 10(5) M-1. The precise carbohydrate binding specificity was studied using hemagglutinating inhibition assay and immobilized TJA-I. A series of oligosaccharides possessing a Neu5Ac alpha 2-->6Gal beta 1-->4GlcNAc or HSO3(-)-->6Gal beta 1-->4GlcNAc group showed tremendously stronger binding ability than oligosaccharides with a Gal beta 1-->4GlcNAc group, indicating that TJA-I basically recognizes an N-acetyllactosamine residue and that the binding strength increases on substitution of the beta-galactosyl residue at the C-6 position with a sialic acid or sulfate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of DNA oligonucleotides containing 5-(mercaptomethyl)-2'-deoxyuridine moieties

Recently thiolated oligonucleotides have attracted significant interest due to their ability to efficiently undergo stable bond formation with gold nanoparticles and surfaces to form DNA conjugates. In this respect we became interested in the synthesis of oligonucleotides that bear short thioalkyl functions located at the nucleobase. Here we present a strategy for the synthesis of DNA oligonucleotides that bear 5-(mercaptomethyl)-2'-deoxyuridine moieties. The building blocks were synthesized in a straightforward manner from thymidine. Only moderate changes of standard protocols for automated DNA synthesis are required for the generation of modified oligonucleotides containing the thiolated building blocks.     

Insight into multi-site mechanisms of glycosyl transfer in (1-->4)beta-D-glycans provided by the cereal mixed-linkage (1-->3),(1-->4)beta-D-glucan synthase.

Synthases of cellulose, chitin, hyaluronan, and all other polymers containing (1-->4)beta-linked glucosyl, mannosyl and xylosyl units have overcome a substrate orientation problem in catalysis because the (1-->4)beta-linkage requires that each of these sugar units be inverted nearly 180 degrees with respect to its neighbors. We and others have proposed that this problem is solved by two modes of glycosyl transfer within a single catalytic subunit to generate disaccharide units, which, when linked processively, maintain the proper orientation without rotation or re-orientation of the synthetic machinery in 3-dimensional space. A variant of the strict (1-->4)beta-D-linkage structure is the mixed-linkage (1-->3),(1-->4)beta-D-glucan, a growth-specific cell wall polysaccharide found in grasses and cereals. beta-Glucan is composed primarily of cellotriosyl and cellotetraosyl units linked by single (1-->3)beta-D-linkages. In reactions in vitro at high substrate concentration, a polymer composed of almost entirely cellotriosyl and cellopentosyl units is made. These results support a model in which three modes of glycosyl transfer occur within the synthase complex instead of just two. The generation of odd numbered units demands that they are connected by (1-->3)beta-linkages and not (1-->4)beta-. In this short review of beta-glucan synthesis in maize, we show how such a model not only provides simple mechanisms of synthesis for all (1-->4)beta-D-glycans but also explains how the synthesis of callose, or strictly (1-->3)beta-D-glucans, occurs upon loss of the multiple modes of glycosyl transfer to a single one.     

Purification and characterization of a lactonase from Burkholderia sp. R-711, that hydrolyzes (R)-5-oxo-2-tetrahydrofurancarboxylic acid

A lactonase hydrolyzing (R)-5-oxo-2-tetrahydrofurancarboxylic acid to D-alpha-hydroxyglutaric acid was purified 170-fold with 2% recovery to near homogeneity from crude extracts of Burkholderia sp. R-711, which had been isolated as a bacterium able to assimilate (R)-5-oxo-2-tetrahydrofurancarboxylic acid. The molecular mass was estimated to be 33 kDa by gel filtration. The purified preparation migrated as a single band of molecular mass 38 kDa upon SDS-PAGE. The maximum activity was observed at pH 7.0-8.0 and 35-40 degrees C. The enzyme required no added cofactors or metal ions; the activity was inhibited to 60-100% by SH-blocking reagents, but was not affected by metal-chelating reagents. The enzyme showed lower activity and affinity toward (S)-5-oxo-2-tetrahydrofurancarboxylic acid, but did not act on other natural and synthetic lactones tested.