Preparation of chitooligosaccharides from chitosan by a complex enzyme

Chitosan of 24% degree of acetylation was depolymerized by a mixture of cellulase, alpha amylase, and proteinase to give the title oligosaccharides. The removal of products by membrane separation permitted yield maximization of products having degree of polymerization in the 3-10 range. (C) 1999 Elsevier Science Ltd. All rights reserved.

Capillary zone electrophoresis investigation of interactions between granulocyte-colony stimulating factor and dextran sulfate/carrageenan oligosaccharide

The interactions between granulocyte-colony stimulating factor (G-CSF) and dextran sulfate/kappa-carrageenan oligosaccharide were studied by capillary zone electrophoresis. Dextran sulfate could strongly interact with G-CSF and the complex was detected. The binding constant and stoichiometry were determined to be 1.2x10(6) (mol/L)(-1) and 3:1, respectively. However, the interaction between K-carrageenan oligosaccharide and G-CSF was not found.

Improving Nucleation in the Fabrication of High-Quality 3D Macro-Porous Copper Film through The Surface-Modification of A Polystyrene Colloid-Assembled Template

A new approach is developed to the fabrication of high-quality three-dimensional macro-porous copper films. A highly-ordered macroporous copper film is successfully produced on a polystyrene sphere (PS) template that has been modified by sodium dodecyl sulfate (SDS). It is shown that this procedure can change a hydrophobic surface of PS template into a hydrophilic surface. The present study is devoted to the influence of the electrolyte solution transport on the nucleation process. It is demonstrated that the permeability of the electrolyte solution in the nanochannels of the PS template plays an important role in the chemical electrodeposition of high-quality macroporous copper film. The permeability is drastically enhanced in our experiment through the surface modi. cation of the PS templates. The method could be used to homogeneously produce a large number of nucleations on a substrate, which is a key factor for the fabrication of the high-quality macroporous copper film.

Electrostatic Interactions Between Glycosaminoglycan Molecules

The electrostatic interactions between nearest-neighbouring chondroitin sulfate glycosaminoglycan (CS-GAG) molecular chains are obtained on the bottle brush conformation of proteoglycan aggrecan based on an asymptotic solution of the Poisson-Boltzmann equation the CS-GAGs satisfy under the physiological conditions of articular cartilage. The present results show that the interactions are associated intimately with the minimum separation distance and mutual angle between the molecular chains themselves. Further analysis indicates that the electrostatic interactions are not only expressed to be purely exponential in separation distance and decrease with the increasing mutual angle but also dependent sensitively on the saline concentration in the electrolyte solution within the tissue, which is in agreement with the existed relevant conclusions.

Equivalent Model Of Expansion Of Cement Mortar Under Sulphate Erosion

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is performed. The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

Damage Evolution In Cement Mortar Due To Erosion Of Sulphate

Ultrasonic technique is used to detect the velocity change of stress wave propagated in the cement mortar immersed in the solution of sodium sulfate for 425 days. Also the density change of specimens at different erosion time is measured. By curve fitting, the effect of solutions' concentration and water/cement ratio on the damage evolution is analyzed. The SEM observation on the growth of delayed ettringite is also performed. It shows that the damage evolution of specimens attacked by sulphate solution is dominantly induced by the nucleation and growth of delayed ettringite, and the average size of microvoids in cement mortar affects the damage evolution significantly. (c) 2008 Elsevier Ltd. All rights reserved.

EQUIVALENT MODEL OF EXPANSION OF CEMENT MORTAR UNDER SULPHATE EROSION

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is performed. The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

壳聚糖衍生物抑菌性能及机理的研究

壳聚糖是一种天然的聚阳离子氨基多糖，由甲壳素经脱乙酰反应得到。作为天然可再生资源，壳聚糖以其特有的安全无毒、可生物降解、生物相容等特性，在农业、生物工程、制药、环保等领域引起广泛关注。随着对壳聚糖研究的不断深入，壳聚糖的抑菌活性及机理成为研究热点之一，但是，大多集中于壳聚糖分子量和脱乙酰度对其抑菌活性的影响，而对壳聚糖衍生物的抑菌性能及机理研究较少。本文合成了N–季铵盐，N,O–季铵盐，羧甲基壳聚糖希夫碱及其铜配合物，壳聚糖有机酸盐，并对它们的抑菌活性进行了研究，同时探讨了引入基团与抑菌活性之间的关系。 测定了壳聚糖及其季铵盐对黄瓜枯萎病菌、黄瓜炭疽病菌和桃褐腐病菌的抑制活性，结果表明壳聚糖季铵盐的抑制活性高于壳聚糖，其中，抑制活性最强的是N–异丁基–N,N–二甲基壳聚糖，当样品浓度为500μg/mL时，对三种病原菌的抑制率分别为：67.52%、70.42%和76.25%。壳聚糖分子带正电荷的氨基可以与菌体表面带负电的物质作用，导致菌体死亡，而壳聚糖季铵盐分子中的正电性可以加强这种作用，从而增强抑菌活性，而且随着正电性的增强，抑菌活性增强。 为了进一步研究壳聚糖季铵盐的正电性与其抑菌活性的关系，合成了含有氟、溴、氯吸电子基团苯环取代的壳聚糖季铵盐，通过计算分别得到取代基团的电负性以及氨基正电性。结果表明，随着取代基团电负性的增强，季铵盐氨基正电性增强，抑菌活性增强。其中，抑菌活性最强的是N–(2–氟)苄基–N,N–二甲基壳聚糖，当样品浓度为500μg/mL时，对三种病原菌的抑制率分别为：80.85%、100%和100%。 将壳聚糖的–NH2与有机酸的–H通过离子键结合制备得到了系列的固态壳聚糖有机酸盐：壳聚糖甲酸盐、壳聚糖乙酸盐、壳聚糖丙酸盐、壳聚糖丁酸盐和壳聚糖戊酸盐，抑菌活性结果表明，随着衍生物链长的增加，抑菌活性增强，而且衍生物抑菌活性与取代基团的电负性成正相关。 以羧甲基壳聚糖为原料，合成了羧甲基壳聚糖希夫碱及其铜配合物，各类衍生物的抑菌活性强弱顺序如下：羧甲基壳聚糖希夫碱铜配合物>羧甲基壳聚糖希夫碱>羧甲基壳聚糖，从而说明了基团的相互增效作用能增强衍生物的抑菌活性。 以N–季铵盐为原料，以环氧丙基三甲基氯化铵为改性剂合成了具有–N+(CH3)2R和–N+(CH3)3两种基团的N,O–季铵盐，抑菌活性结果表明，N,O–季铵盐的抑菌活性

ISOLATION AND PROPERTIES OF A BLOOD-COAGULATION FACTOR-X ACTIVATOR FROM THE VENOM OF KING COBRA (OPHIOPHAGUS HANNAH)

A specific blood coagulation factor X activator was purified from the venom of Ophiophagus hannah by gel filtration and two steps of FPLC Mono-Q column ion-exchange chromatography. It showed a single protein band both in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and alkaline polyacrylamide gel electrophoresis. The mol. wt was estimated to be 62,000 in non-reducing conditions and 64,500 in reducing conditions by SDS-PAGE. The isoelectric point was found to be pH 5.6. The enzyme had weak amidolytic activities toward CBS 65-25, but it showed no activities on S-2266, S-2302, thrombin substrate S-2238, plasmin substrate S-2251 or factor Xa substrate S-2222. It had no arginine esterase activity toward substrate benzoylarginine ethylester (BAEE). The enzyme activated factor X in vitro and the effect was absolutely Ca2+ dependent, with a Hill coefficient of 6.83. It could not activate prothrombin nor had any effect on fibrinogen and thus appeared to act specifically on factor X. The procoagulant activity of the enzyme was almost completely inhibited by serine protease inhibitors like PMSF, TPCK and soybean trypsin inhibitor; partially inhibited by L-cysteine. Metal chelator EDTA did not inhibit its procoagulant activity. These results suggest that the factor X activator from O. hannah venom is a serine protease.