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Dextran synthesis has been studied since the Second World War, when it was used as blood plasma expander. This polysaccharide
composed of glucose units is linked by an α-1,6-glucosidic bond. Dextransucrase is a bacterial extra cellular enzyme, which
promotes the dextran synthesis from sucrose. When, besides sucrose, another substrate (acceptor) is also present in the reactor,
oligosaccharides are produced and part of the glucosyl moieties from glucose is consumed to form these acceptor products,
decreasing the dextran yield. Although dextran enzymatic synthesis has been extensively studied, there are few published studies
regarding its molecular weight distribution. In this work, the effect of maltose on yield and dextran molecular weight synthesized
using dextransucrase from Leuconostoc mesenteroides B512F, was investigated. According to the obtained results, maltose is not able to control and reduce dextran molecular weight
distribution and synthesis carried out with or without maltose presented the same molecular weight distribution profile. 相似文献
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Hisao Tomida Takeshi Fujii Nobuko Furutani Akihiro Michihara Taira Yasufuku Kenji Akasaki Toru Maruyama Masaki Otagiri Janusz M. Gebicki Makoto Anraku 《Carbohydrate research》2009,344(13):1690-1696
Chitosan, a cationic polysaccharide, is widely employed as dietary supplement and in pharmacological and biomedical applications. Although numerous studies have focused on its applications as pharmaceutical excipients or bioactive reagents, relationships between molecular weight (Mr) and biological properties remain unclear. The focus of this study was on the antioxidant properties of several Mr chitosans. We measured the ability of seven Mr chitosans (CT1; 2.8 kDa, CT2; 17.0 kDa, CT3; 33.5 kDa, CT4; 62.6 kDa, CT5; 87.7 kDa, CT6; 604 kDa, CT7; 931 kDa) to protect plasma protein from oxidation by peroxyl radicals derived from 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH). A comparison of the antioxidant action of high Mr chitosans (CT6–CT7) with that of low Mr chitosans (CT1–CT5) showed that low Mr chitosans (CT1–CT5) were more effective in preventing the formation of carbonyl groups in plasma protein exposed to peroxyl radicals. AAPH substantially increases plasma protein carbonyl content via the oxidation of human serum albumin (HSA). We also measured the ability of these chitosans to protect HSA against oxidation by AAPH. Low Mr chitosans (CT1–CT5) were found to effectively prevent the formation of carbonyl groups in HSA, when exposed to peroxyl radicals. Low Mr chitosans were also good scavengers of N-centered radicals, but high Mr chitosans were much less effective. We also found a strong correlation between antioxidant activity and the Mr of chitosans in vitro. These activities were also determined by using the ‘TPAC’ test. These results suggest that low Mr chitosans (CT1–CT3) may be absorbed well from the gastrointestinal tract and inhibit neutrophil activation and oxidation of serum albumin that is frequently observed in patients plasma undergoing hemodialysis, resulting in a reduction in oxidative stress associated with uremia. 相似文献
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Zhanyong Guo Ronge Xing Song Liu Zhimei Zhong Xia Ji Lin Wang Pengcheng Li 《Carbohydrate polymers》2008,71(4):694-697
Quaternized chitosan derivatives with different molecular weights were synthesized in the laboratory. Subsequent experiments were conducted to test their antifungal activities against Botrytis cinerea Pers. (B. cinerea pers.) and Colletotrichum lagenarium (Pass) Ell.et halst (C. lagenarium (Pass) Ell.et halst). Our results indicate that quaternized chitosan derivatives have stronger antifungal activities than chitosan. Furthermore, quaternized chitosan derivatives with high molecular weight are shown to have even stronger antifungal activities than those with low molecular weight. 相似文献
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Average molecular weight and molecular weight distribution of agarose and agarose-type polysaccharides 总被引:4,自引:0,他引:4
Cyrille Rochas
Marc Lahaye
《Carbohydrate polymers》1989,10(4):289-298A procedure to determine the absolute weight-average molecular weight and molecular weight distribution of agarose and agarose-type polysaccharides by aqueous size-exclusion chromatography coupled with low-angle laser light scattering is described. The molecular weights of the majority of the commercial samples investigated were between 80 000 and 140 000 with a polydispersity lower than 1·7. In contrast, most of the laboratory-extracted agarose-type polysaccharides had lower molecular weights. 相似文献
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The structure of pyrenetetrasulfonate intercalated with hydrotalcite, having the formula [Zn0.68Al0.32(OH)2][(C16H6O12S4)0.08 · x H2O], was proposed based on molecular simulations combined with experimental data (X-ray powder diffraction, thermogravimetry).
Calculations were done for samples kept at various relative humidities (0%, 84%, 98%). The appropriate models were selected
from comparison of calculated and measured diffraction patterns. Modelling revealed the arrangement of pyrenetetrasulfonate
anions, and the positions and the amount of water molecules in the interlayer space of the host structure. The results confirmed
a large variability in the arrangement of the guest species. In the sample without water molecules (0% RH), pyrenetetrasulfonate
anions formed a layer at the centre of the interlayer distance. For the sample kept at 84% RH, the anions formed two layers
at the thirds of the interlayer. For the sample kept at 98% RH, the anions became tilted with respect to the layered double
hydroxides (LDH) layers and are less organised. Water molecules were arranged in three distinct planes: one in the middle
and two at the quarters of interlayer distance. The number of water molecules obtained by the modelling basically agrees with
the water content as measured by thermogravimetry.
Figure Pyrenetetrasulfonate was intercalated into hydrotalcite and equilibrated at various relative humidities. Structural analysis
was performed using molecular simulations based on X-ray and thermogravimetric data 相似文献
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《Bioorganic & medicinal chemistry》2020,28(1):115179
Traditional Chinese Medicine has been widely used in China and is regarded as the most commonly used treatment. As a natural plant used in traditional Chinese Medicine, Basil has various functions associated with a number of its components. There are many compositions in basil including polysaccharides, naphtha, steroids, flavone, coumarins, vitamins, and so on. Among these, polysaccharides play a significant role in based therapeutics. The article summarizes that basil polysaccharides have a lot of biological activities and pharmacological applications, such as their antitumor activity, antioxidant activity, anti-aging activity, immunity enhancement effect, hypolipidemic and anti-atherosclerotic effects, antibacterial effect, treatment of diabetes mellitus, and so on. This review summarized the extraction method, purification method, compositions, pharmacological applications, molecular weight, biological activities, and prospects of basil polysaccharides, providing a basis for further study of basil and basil polysaccharides. 相似文献
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P. Månsson Ö. Jacobsson K.A. Granath 《International journal of biological macromolecules》1985,7(1):30-32
The molecular weight of Na- and K-hyaluronate has been determined by low angle laser light scattering (LALLS) technique. Two preparations of hyaluronate from rooster comb () were investigated. The LALLS was carried out both in a static mode and on the effluent from a column filled with porous gel. In contrast to Sheehan et al.1, no significant difference was found in the molecular weight of viscosity of Na- and K-hyaluronate in 2.0 M salt solutions 相似文献
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Weigent DA 《Cellular immunology》2011,(1):44-52
A substantial body of research exists to support the idea that cells of the immune system produce growth hormone (GH). However, the structure and mechanism of action of lymphocyte-derived GH continues to remain largely unknown. Here we present the results of Western analysis of whole cell extracts showing that different molecular weight isoforms of GH of approximately 100, 65, and 48 kDa can be detected in primary mouse cells of the immune system and in the mouse EL4 cell line. The identity of the 65 and 48 kDa isoforms of GH were confirmed by mass spectrometry. The various isoforms were detected in both enriched T and B spleen cell populations. The large molecular weight isoform appears to reside primarily in the cytoplasm, whereas the lower molecular weight 65 and 48 kDa isoforms were detected primarily in the nucleus. These results also suggest that GH isoforms are induced by oxidative stress. In EL4 cells overexpressing GH, the expression of luciferase controlled by a promoter containing the antioxidant response element is increased almost threefold above control. The data suggest that the induction of isoforms of the GH molecule in cells of the immune system may be an important mechanism of adaptation and/or protection of lymphoid cells under conditions of oxidative stress. 相似文献
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Goetz H Kuschel M Wulff T Sauber C Miller C Fisher S Woodward C 《Journal of biochemical and biophysical methods》2004,60(3):281-293
Protein analysis techniques are developing fast due to the growing number of proteins obtained by recombinant DNA techniques. In the present paper we compare selected techniques, which are used for protein sizing, quantitation and molecular weight determination: sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), lab-on-a-chip or microfluidics technology (LoaC), size exclusion chromatography (SEC) and mass spectrometry (MS). We compare advantages and limitations of each technique in respect to different application areas, analysis time, protein sizing and quantitation performance. 相似文献
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A rapid method was developed to determine the molecular weight (Mn) of β-limit dextrin and dextrans (Leuconostoc mesenteroides) using a reducing power approach. The Mn of the β-limit dextrin was also estimated from high performance liquid chromatography (HPLC). Chromatograms were pre-calibrated with the dextrans. The three dextrins had a Mn of 2.09, 2.40 and 2.63 × 105 using the reducing method and 4.80, 5.90 and 2.80 × 105 by HPLC. The method could be employed to estimate Mn of dextrins where chromatographic systems were not available. 相似文献
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Correlation between antitumor activity, molecular weight, and conformation of lentinan 总被引:19,自引:0,他引:19
A (1-->3)-beta-D-glucan having (1-->6) branching (L-FV-IB) from Lentinus edodes in water was degraded into seven fractions of different molecular weights by ultrasonic irradiation, and each was further fractionated into three parts, by precipitation from water into acetone at room temperature. The weight-average molecular weight (M(w)), radius of gyration ((z)(1/2)), and intrinsic viscosity ([eta]) of lentinan and its fractions in 0.9% NaCl aqueous solution and dimethyl sulfoxide (Me(2)SO) were determined by size-exclusion chromatography combined with multi-angle laser light scattering (SEC-LLS), LLS, and viscometry. Analysis of M(w), [eta], and (z)(1/2) in terms of known theory for worm-like chains yielded 2240 +/- 100 nm(-1), and 100 +/- 10 nm for molar mass per unit contour length (M(L)), and persistence length (q), respectively, corresponding with theoretical data for triple-helical chains. The [alpha](D) of lentinan in water-Me(2)SO mixtures indicated an order-disorder transition. The results indicated that lentinan exists as a triple helix in 0.9% NaCl aqueous solution and as a single flexible chain in Me(2)SO. Assays in vivo and in vitro against the growth of Sarcoma 180 solid tumor as well as the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method for lentinan showed that the triple-helix sample exhibited a relatively high inhibition ratio. Interestingly, the triple-helix lentinan with M(w) of 1.49 x 10(6) exhibited the highest antitumor activity in vivo, having an inhibition ratio (xi) of 49.5%, close to that of 5-fluorouracil (xi = 50.5%), whereas the bioactivity (xi = 12.3%) of its single flexible chains almost disappeared. The triple-helix conformation plays an important role in enhancing the antitumor effects of lentinan. 相似文献
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Effects of molecular weight and deacetylation degree of chitin/chitosan on wound healing 总被引:4,自引:0,他引:4
Tatsuya Minagawa Yasuhiko Okamura Yoshihiro Shigemasa Saburo Minami Yoshiharu Okamoto 《Carbohydrate polymers》2007,67(4):640-644
We studied the effects of chitin/chitosan on wound healing with reference to chemical properties using a linear incisional wound model in rats. Wound break strength of the chitosan group (D-glucosamine (GlcN), chito-oligosaccharide (COS), chitosan) was higher than the chitin group (N-acetyl-D-glucosamine (GlcNAc), chiti-oligosaccharide (NACOS), chitin). Collagenase activity was also higher in the chitosan group than the chitin group. There was no significant change between the concentration of the sample and the break strength and collagenase activity in all samples. In histological findings, collagen fibers run perpendicular against the incisional line in the oligosaccharide group (NACOS, COS), and many activated fibroblasts were observed around the wound in the chitosan group. As for the deacetylation degree, the higher the deacetylation degree becomes, the more the stronger the break strength becomes. Also, activated fibroblasts appeared more in the higher deacetylation degree. 相似文献
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S. A. Visser 《Plant and Soil》1985,87(2):209-221
Summary Viscosities were investigated of solutions of fulvic and humic acid molecular weight fractions of aquatic, terrestrial and microbial origin. Aquatic fulvic and humic acid molecules were, at pH 7, more voluminous than other types of humic compounds of similar molecular weight. It would appear that in low molecular weight non-aquatic humic matter, more inter- than intra-molecular bonding is present, with increasing molecular weight the bonding becomes more intra-molecular. Differences between average molecular weight values as obtained by an ultrafiltration method (Amicon) and by viscosimetry ranged from –18.7 to 18.5%. The largest deviations were in the low molecular weight range (<5,500 daltons). Higher molecular weight humics (in particular humic acids) appeared to have a more elongated structure than lower molecular weight material (in particular fulvic acids). Indications were obtained that on hydration humic moleculars become more elongated. 相似文献
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Cereal beta-glucans can form aggregates in aqueous solution. The presence of aggregates in cereal beta-glucan solutions led to inaccurate determination of molecular weights and it was believed that intermolecular hydrogen bonding caused the aggregation. To eliminate aggregates, a carbanilation method for molecular weight determination of cereal beta-glucans was developed. Wheat beta-glucan samples were selected for investigation. The carbanilation method can prevent intermolecular hydrogen bonding by blocking hydroxyl groups with phenyl carbamate groups. The carbanilates of cereal beta-glucans were prepared by the reaction of cereal beta-glucans with phenylisocyanate catalyzed by DMSO and pyridine. To avoid degradation during the carbanilation reaction, relatively mild conditions were used, which led to incomplete substitution (DS: approximately 2). However, after the carbanilation reaction, the carbanilates dissolved completely in 1,4-dioxane solution without any detectable aggregates, which allowed accurate molecular weight determination. The degree of substitution (DS) of carbanilates was determined by both a nitrogen content method and an FT-IR method. The FT-IR method proved to be the more effective for DS estimation. Using this method, the converted molecular weights of cereal beta-glucans were in good agreement with the results measured in 0.5M NaOH solution, which previously was shown to be a good solvent for cereal beta-glucans. After the carbanilation reaction, conformational changes of carbanilates were studied by static and dynamic light scattering techniques. The fractal dimension (d(f)=2.27) and the structure sensitive parameters (rho >2) suggested a porous globular structure for partially carbanilated beta-glucans. 相似文献
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Hitomi Kumagai William MacNaughtan Imad A. Farhat John R. Mitchell 《Carbohydrate polymers》2002,48(4):341-349
The influence of less than 1% of κ-carrageenan on the mobility of glucose syrup was studied in the context of the glass–rubber transition using proton NMR relaxometry. Glass-transition temperatures, (Tg) were measured by differential scanning calorimetry (DSC) on glucose syrup samples containing 0 or 0.9% κ-carrageenan, between 0 and 1.4% KCl, and at water contents from 3.5 to 16% (wwb). Potassium chloride was added to vary the extent of gelation of the carrageenan in order to assess the effect of the biopolymer network on molecular mobility.
Contrary to the reported increase of the rheologically determined glass-transition temperature, in the presence of gelling agents, the addition of 0.9% κ-carrageenan to glucose syrup with and without KCl, had no effect on the DSC measured Tg. In addition, there was no effect on molecular mobility in the glassy region. The presence of carrageenan only significantly affected the mobile part of the NMR free induction decay at relatively high temperatures. 相似文献