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At least 343 records · Page 19Linked to original sources
PubMed2006

Doxorubicin release from core-shell type nanoparticles of poly(DL-lactide-co-glycolide)-grafted dextran.

In this study, we prepared core-shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer with varying graft ratio of PLGA. The synthesis of the DexLG copolymer was confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy. The DexLG copolymer was able to form nanoparticles in water by self-aggregating process, and their particle size was around 50 nm approximately 300 nm according to the graft ratio of PLGA. Morphological observations using a transmission electron microscope (TEM) showed that the nanoparticles of the DexLG copolymer have uniformly spherical shapes. From fluorescence probe study using pyrene as a hydrophobic probe, critical association concentration (CAC) values determined from the fluorescence excitation spectra were increased as increase of DS of PLGA. 1H-NMR spectroscopy using D2O and DMSO approved that DexLG nanoparticles have core-shell structure, i.e. hydrophobic block PLGA consisted inner-core as a drug-incorporating domain and dextran consisted as a hydrated outershell. Drug release rate from DexLG nano-particles became faster in the presence of dextranase in spite of the release rate not being significantly changed at high graft ratio of PLGA. Core-shell type nanoparticles of DexLG copolymer can be used as a colonic drug carrier. In conclusion, size, morphology, and molecular structure of DexLG nanoparticles are available to consider as an oral drug targeting nanoparticles.

Administration, Oral↗
PubMed1998

Synthesis and properties of dextran-5-aminosalicylic acid ester as a potential colon-specific prodrug of 5-aminosalicylic acid.

Dextran-5-aminosalicylic acid ester (dextran-5-ASA) was synthesized as a colon-specific prodrug of 5-aminosalicylic acid (5-ASA) which is active against inflammatory bowel diseases. Chemical stability of dextran-5-ASA in the bath of pH 1.2 or 6.8 was investigated at 37 degrees C for 6 hrs, and 5-ASA was not released on such conditions. Depolymerization (%) of dextran-5-ASA by dextranase with the degree of substitution (DS) of 18, 23, or 30 was 92, 62 or 45 in 8 hrs respectively, but was not affected by the MW of dextran (9,000, 40,600, 80,200 or 580,000). Distribution of 5-ASA in dextran, determined by gel filtration chromatography, appeared to be relatively uniform. Incubation of dextran-5-ASA (DS 18) in cecal contents of rats released 20% (28 g) and 35% (49 g) of 5-ASA in 8 hrs and 24 hrs, respectively, but no 5-ASA was liberated from small intestinal contents.

Aminosalicylic Acids↗
PubMed1998

[Excessive tissue storage of colloids in the reticuloendothelial system].

In addition to renal elimination and gastrointestinal metabolism (amylase; splenic and hepatic dextranase) colloid plasma solutions like dextran and hydroxyethyl starch deposit in tissues, especially in the reticuloendothelial system (RES). This tissue storage is limited in time (weeks to months), is influenced by the employed solution and other factors (lysosomes) and has usually no clinical importance (no RES blockade). We report here a case study of a patient with sepsis (lung, liver and kidney failure) who had an overload of the RES with colloids while being treated with dextran (molecular weight 40,000 and 70,000 daltons) and hydroxyethyl starch (mw 450,000 daltons, molar substitution 0,7) for 5 weeks. Autopsy showed parenchymal and reticuloendothelial cells of liver, lung, kidney and spleen with a large amount of colloid mass inclusions and altered organ morphology. This storage may have impaired ventilation, transport of bile acids and renal function. A possible role of tissue storage of colloids in organ failure is discussed.

Blood Substitutes↗
PubMed1996

Extracellular alpha-Glucosidase with Dextran-Hydrolyzing Activity from the Thermophilic Fungus, Thermomyces lanuginosus

The thermophilic fungus Thermomyces lanuginosus, which is able to use dextran as primary carbon source for growth, excreted during the early phases of growth an enzyme activity capable of degrading dextran. The activity peaked at 22 h and decreased rapidly after the culture entered the stationary phase, probably caused by protease activity. Results from growth on a number of different carbon sources showed that polymer carbohydrates yielded the highest dextranase activities. On the basis of the substrate specificity and the release of glucose in the alpha-anomeric form from the hydrolysis of maltose, it is proposed that the enzyme responsible for the necessary degradation of dextran to smaller saccharides is an alpha-glucosidase.

Journal Article↗
PubMed1983

A D-glucosylated form of dextransucrase: preparation and characteristics.

Dextransucrase was treated with [14C]sucrose, and the product applied to gel-permeation columns. In the absence of the detergents SDS and Triton X-100, poor recovery of enzyme was observed; however, that enzyme which was recovered was labeled. In the presence of detergents, recovery was increased, but the material appeared to be a large aggregate (mol. wt. greater than 5 X 10(6) ). In addition, the ratio of D-glucose to enzyme suggested that a polymer had been formed. Disc-gel electrophoresis in the presence of a mixture of SDS and Triton X-100 showed similar results, and indicated that the aggregate was disrupted upon treatment with dextranase. Native enzyme that had been immobilized on hydroxylapatite could also be labeled with [14C]sucrose, and the labeling followed saturation kinetics. The labeled protein could be released from the gel with 8M urea, but was aggregated. Radioactive sugars, free from protein, could be released by heating the labeled enzyme. The sugars released consisted of a mixture of D-glucose with oligosaccharides having an average chain-length of 17 D-glucosyl residues. The significance of these observations is discussed.

Chromatography, Gel↗
PubMed1988

Reduction of the adherence of Streptococcus sobrinus insoluble alpha-D-glucan by endo-(1----3)-alpha-D-glucanase.

Insoluble alpha-D-glucan, previously formed on a glass surface from sucrose by the action of cell-free D-glucosyltransferases of Streptococcus sobrinus OMZ176, was significantly removed by a purified preparation of endo-(1----3)-alpha-D-glucanase (mutanase) from a strain of Pseudomonas sp. Almost complete dissociation of adherent glucan occurred at the highest enzyme concentration (40 mU/mL) tested. Synthesis and de novo adherence on glass of the glucan was markedly inhibited by the presence of mutanase, even at low concentrations (4 mU/mL or less). When compared to native glucan, the mutanase-modified glucan samples (a) contained lower proportion of D-(1----3) linkages; (b) showed lower susceptibility to mutanase and higher susceptibility to (1----6)-alpha-D-glucanase (dextranase); (c) contained larger amounts of low-molecular-weight fractions; (d) had lower intrinsic viscosities; (e) showed higher S. sobrinus cell-agglutinating activities; and (f) consisted of looser entwinement of coalescent single-stranded fibrils (a major component) and shorter double-stranded fibrils (a minor one).

Adhesiveness↗
PubMed1976

Variability of Alternaria alternata: biochemical and immunological characteristics of culture filtrates from seven isolates.

Biochemical variability of culture filtrates from the common allergenic mold Alternaria alternata was studied. Differences between culture filtrates from 7 different isolates and between 4 batches of culture filtrate from the same isolate were observed, suggesting the unreliability of presently employed biochemical methods in the routine standardization of mold allergens and the possibility of difficulties in developing standard techniques for their purification. Dextranases, cellulases, and agarases, found in one culture filtrate, may be a further source of problems in laboratory techniques employing A. alternata. The proportions of nitrogen:carbohydrate:dialyzed dry weight were different in culture filtrates from each isolate. Polysaccharides in culture filtrates from 3 of the 7 isolated contained glucose, mannose, xylose, galactose, and a fifth, unidentified sugar. Polysaccharides from one isolate lacked xylose, and the fifth sugar was not demonstrable in 4 of the isolates. Despite the biochemical differences, extensive antigenic cross-reactivity between different isolates was found in precipitin studies and inhibition of antibody binding.

Alternaria↗
PubMed1994

Production and selection of mutants of Leuconostoc mesenteroides constitutive for glucansucrases.

After chemical mutagenesis using ethyl methane sulfonate, we isolated mutants constitutive for glucansucrases from Leuconostoc mesenteroides NRRL B-512FM, B-1142, and B-1355. Those mutants produced glucansucrases when grown on D-glucose as well as on sucrose. They produced higher glucansucrase activities (3 to 22 times) when grown on D-glucose than the parent strains grown on sucrose. Glucansucrases from mutants B-1355C and B-1142C grown on glucose formed glucans that were highly resistant to Penicillium dextranase hydrolysis. Mutant B-512FMC dextransucrase formed the same kind of dextran as the parent strain; however, it showed higher thermal stability, even when dextran was absent.

Biotechnology↗
PubMed1984

Stabilization of dextransucrase from Leuconostoc mesenteroides NRRL B-512F by nonionic detergents, poly(ethylene glycol) and high-molecular-weight dextran.

Dextransucrase (sucrose: 1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase, EC 2.4.1.5) (3 IU/ml culture supernatant) was obtained by a modification of the method of Robyt and Walseth (Robyt, J.F. and Walseth, T.F. (1979) Carbohydr. Res. 68, 95-111) from a nitrosoguanidine mutant of Leuconostoc mesenteroides NRRL B-512F selected for high dextransucrase production. Dialyzed, concentrated culture supernatant (crude enzyme) was treated with immobilized dextranase (EC 3.2.1.11) and chromatographed on a column of Bio-Gel A-5m. The resulting, purified enzyme lost activity rapidly at 25 degrees C or on manipulation, as did the crude enzyme when diluted below 1 U/ml. Both enzyme preparations could be stabilized by low levels of high-molecular-weight dextran (2 micrograms/ml), poly(ethylene glycol) (e.g., 10 micrograms/ml PEG 20 000), or nonionic detergents (e.g., 10 micrograms/ml Tween 80). The stabilizing capacity of poly(ethylene glycol) and of dextran increased with molecular weight. Calcium had no stabilizing action in the absence of other additions, but reduced the inactivation that occurred in the presence of 0.5% bovine serum albumin or high concentrations (greater than 0.1%) of Triton X-100. In summary, dextransucrase could be stabilized against activity losses caused by heating or by dilution through the addition of low concentrations of nonionic polymers (dextran, PEG 20000, methyl cellulose) or of nonionic detergents at or slightly below their critical micelle concentrations.

Calcium↗
PubMed1990

An automated spectrophotometric flow-injection procedure for the determination of cellulase activity in bioreactor preparations.

A spectrophotometric procedure for the determination of cellulase activity in precipitated bioreactor preparations and culture filtrates is described. It is based on the determination of reducing sugar produced by the action of the enzyme on carboxymethylcellulose. The reducing sugar is derivatized with p-aminobenzoyl-hydrazide and permits a limit of detection of 0.1 U ml-1 cellulase in the presence of background sugar, with a sampling rate of 5 h-1. The method can readily be applied to the determination of any carbohydrase acting on soluble substrates and producing reducing sugars, e.g. amylase, dextranase, xylanase, glucanase and polygalacturonase.

Calibration↗
PubMed2004

Enzymatic synthesis of two salicin analogues by reaction of salicyl alcohol with Bacillus macerans cyclomaltodextrin glucanyltransferase and Leuconostoc mesenteroides B-742CB dextransucrase.

Beta-Salicin is a naturally occurring glycoside found in the bark of poplar and willow trees. Ancient man used it as an analgesic and antipyretic. It has a D-glucopyranose unit attached by a beta-linkage to the phenolic hydroxyl of salicyl alcohol. Two new salicin analogues have been enzymatically synthesized by transglycosylation reactions: (a) by the reaction of Bacillus macerans cyclomaltodextrin glucanyltransferase with cyclomaltohexaose and salicyl alcohol, followed by reactions with alpha amylase and glucoamylase to give D-glucopyranose attached by an alpha-linkage to the phenolic hydroxyl of salicyl alcohol as the major product, alpha-salicin; and (b) by the reaction of Leuconostoc mesenteroides B-742CB dextransucrase with sucrose and salicyl alcohol, followed by reactions with dextranase and glucoamylase to give alpha-d-glucopyranose attached to the primary alcohol hydroxyl of salicyl alcohol as the major product, alpha-isosalicin.

Bacillus↗
PubMed2005

An enzymatically produced novel cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->} (cyclic maltosyl-(1-->6)-maltose), from starch.

A bacterial strain M6, isolated from soil and identified as Arthrobacter globiformis, produced a novel nonreducing oligosaccharide. The nonreducing oligosaccharide was produced from starch using a culture supernatant of the strain as enzyme preparation. The oligosaccharide was purified as a crystal preparation after alkaline treatment and deionization of the reaction mixture. The structure of the oligosaccharide was determined by methylation analysis, mass spectrometry, and (1)H and (13)C NMR spectroscopy, and it was demonstrated that the oligosaccharide had a cyclic structure consisting of four glucose residues joined by alternate alpha-(1-->4)- and alpha-(1-->6)-linkages. The cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->}, was found to be a novel oligosaccharide, and was tentatively called cyclic maltosyl-maltose (CMM). CMM was not hydrolyzed by various amylases, such as alpha-amylase, beta-amylase, glucoamylase, isoamylase, pullulanase, maltogenic alpha-amylase, and alpha-glucosidase, but hydrolyzed by isomalto-dextranase to give rise to isomaltose. This is the first report of the cyclic tetrasaccharide, which has alternate alpha-(1-->4)- and alpha-(1-->6)-glucosidic linkages.

Arthrobacter↗
PubMed2004

Cloning and expression of Lipomyces starkeyi alpha-amylase in Escherichia coli and determination of some of its properties.

The Lipomyces starkeyi alpha-amylase (LSA) gene encoding soluble starch-degrading alpha-amylase was cloned and characterized from a derepressed and partially constitutive mutant for both dextranase and amylase activities. The nucleotide (nt) sequence of the cDNA fragment reveals an open reading frame of 1944 bp encoding a 619 amino acid (aa) mature protein (LSA) with a calculated molecular weight of 68.709 kDa that was estimated to be about 73 kDa, including His tag (4 kDa) based on SDS-PAGE (10% acrylamide gel), activity staining, and the Western blotting, using anti-amylase-Ab. LSA had a sequence similar to other alpha-amylases in four conserved regions of the alpha-amylase family: (I) (287)DIVVNH(292), (II) (372)GLRIDTVKH(380), (III) (399)GEVFD(403), (IV) (462)FLENQD(467). Polymerase chain reaction and sequence analysis showed one intron of 60 nucleotides in the genomic lsa at positions between 966 and 967 of cDNA. The cloned LSA amylase showed a maximum activity at pH 6 and optimum temperature of 40 (o)C, with greater than 90% stability between pH 5 and pH 8 for 16 h. It was inhibited by Cu(2+) and stimulated by Ca(2+) and Mg(2+). Enzyme activity was not affected by 1 mM EGTA but was inhibited by 1 mM EDTA. LSA did not hydrolyze maltodextrins of G2 to G4, yet formed G2+G3 from G5, G2+G4 or G3+G3 from G6, and G3+G4 from G7. LSA did not hydrolyze soluble starch in the present of 2% (w/v) of acarbose. Kinetics of LSA was carried out by using starch as a substrate and the inhibition type of acarbose was the mixed non-competitive type (ki = 3.4 microM).

Amino Acid Sequence↗
PubMed2005

First isolation of Streptococcus downei from human dental plaques.

In this study, we isolated four bacterial strains grown on mitis-salivarius sucrose bacitracin agar. The strains had similar biochemical characteristics to biotypes I or II of mutans streptococci. The four isolates were identified as Streptococcus downei by 16S rDNA and dextranase gene (dex) sequencing as well as polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) targeting dex. To our knowledge, this is the first report of the isolation and identification of S. downei from dental plaque in humans. The results suggest that S. downei can inhabit the human oral cavity.

Culture Media↗
PubMed2006

The enzymatic activity from the sediment of the Gilau dam reservoir - Cluj county.

The enzymological studies on the sediment of the accumulation lake that has the main purpose of supplying drinking water to the city of Cluj-Napoca and the nearby villages, were aimed at the comprehensive understanding of the complex processes that happen in these habitats of special significance. In the sediment samples the following enzymatic activities have been quantitatively determined: phosphatase, actual and potential dehydrogenase, catalase, urease and protease. Non-enzymatic catalytic activity was also measured. Based on the relative values for the enzymatic activities, the enzymatic indicator of the sediment quality (EISQ) was calculated (ranging from 0.1 to 0.7). The enzymatic activities have been qualitatively determined for maltase, saccharase, lactase, cellobiase, amylase, dextranase, levanase, cellulase and inulinase. The correlation between the enzymatic and bacteriologic potential was statistically calculated.

Enzymes↗
PubMed2006

Beta-lactoglobulin-dextran Maillard conjugates: their effect on interfacial thickness and emulsion stability.

The influence of dextran molecular weight on the steric layer thickness and oil-in-water (O/W) emulsion flocculation stability of beta-lactoglobulin-dextran Maillard conjugates was investigated. Maillard conjugates were formed by reacting beta-lactoglobulin with various molecular weight dextrans (Mw = 18.5-440 kDa) under mild conditions (60 degrees C, 76% RH). Purified Maillard conjugates or beta-lactoglobulin were adsorbed onto latex spheres and the thickness of the adsorbed layer measured using photon correlation spectroscopy. The adsorbed layer thickness was 3 nm for beta-lactoglobulin alone. Attachment of dextran increased adsorbed layer thickness to 5 nm for the conjugate with low molecular weight dextran (Mw = 18.5 kDa) and 20 nm for that with high molecular weight dextran (Mw = 440 kDa). Enzymatic digestion of the adsorbed layers with dextranase reduced the layer to a thickness corresponding to that of beta-lactoglobulin alone. This suggests that the protein segment of the Maillard conjugate anchors the emulsifier to the interface. Attachment of dextran, irrespective of its molecular weight (18.5-440 kDa), increased the stability of emulsions against calcium induced flocculation, demonstrating that a low molecular weight dextran is sufficient for imparting high steric stability. The observation that the steric layer size was controlled by the dextran molecular weight, suggests that the results of layer thickness and emulsion stability should be universal across all globular proteins.

Dextrans↗
PubMed2005

Physico-chemical characterization of polysaccharide-coated nanoparticles.

A series of amphiphilic copolymers (PCL-DEX) made of poly(epsilon-caprolactone) (PCL) side chains grafted onto a dextran (DEX) backbone, was used to modify the surface of PCL nanoparticles. PCL-DEX nanoparticles were prepared by a technique derived from emulsion-solvent evaporation. The purpose of the present study was to investigate the DEX coating (quantification, conformation, mobility) in order to better understand particle surface-protein interactions. The DEX coating was deeply examined using different complementary methods: zeta potential measurement, specific degradation of the DEX shell by dextranase, energy-filtering transmission electron microscopy coupled to image-spectrum electron energy-loss spectroscopy, electronic paramagnetic resonance, high performance size exclusion chromatography as well as nonspecific bovine serum albumin adsorption. All our data together supported a core-shell structure of the nanoparticles, DEX moieties constituting the external coating. The amount of DEX located on the nanoparticle surface was estimated to 70%. The organisation of the shell including chains density and mobility was found to be dramatically influenced by DEX molar mass. The steric repulsion conferred by the presence of DEX at the surface of the nanoparticles decreased the adsorption of albumin. The nanoparticle-protein interaction was, however, greatly influenced by the polysaccharide conformation onto the surface.

Adsorption↗
PubMed1976

Preparation and characterization of a dextran-amylase conjugate.

Bacillus amyloliquefaciens alpha-amylase was attached to dextran after activation of the polysaccharide by using a modification of the cyanogen bromide method. The soluble dextran-amylase conjugate was purified by molecular-sieve chromatography. The conjugated enzyme has greater stability than the unmodified enzyme at low pH values, during heat treatment, and on removal of calcium ions with a chelating agent. Attachment of dextran to alpha-amylase did not alter the Michaelis constant of the enzyme acting on starch. The polysaccharide-enzyme conjugate probably consists of a cross-linked aggregate of many dextran and many enzyme molecules, in which a proportion of the enzyme molecules, although not inactivated, are unable to express their activity, except after dextranase treatment.

Amylases↗