共查询到19条相似文献,搜索用时 57 毫秒
1.
溶菌酶降解壳聚糖条件的研究 总被引:4,自引:0,他引:4
研究了溶茵酶对壳聚糖的降解条件,结果表明:脱乙酰度约70%的壳聚糖较易被溶菌酶水解;水解反应的最适温度为55℃、pH值为4.0,低速摇床振荡对水解有利;在壳聚糖水解初期,溶液中还原糖浓度迅速增加,0.5h后水解速率逐渐减慢,至8h后还原糖浓度的增加已很缓慢;酶解液中还原糖的生成量瞳壳聚糖及溶茵酶浓度的增加而增大,当壳聚糖溶液浓度为20mg/mL、溶茵酶浓度为2.48mg/mL时,水解6h后,还原糖的含量可达6.758mmol/L。水解6h后酶解液中还原糖浓度与壳聚糖的浓度呈线性关系。 相似文献
2.
3.
壳聚糖的配位控制氧化降解及量子化学研究 总被引:2,自引:0,他引:2
提出一种新的壳聚糖降解法——金属配位控制氧化降解法,首先对壳聚糖实行人为特异性结构改造,将壳聚糖转化为壳聚糖金属配合物,再以H2O2对配合物进行氧化降解。对比金属配位控制氧化降解和直接氧化降解的反应结果,表明在相同降解条件下,前一种方法的降解速度明显高于后一种方法,且降解产物分子量分布较后者窄。半经验量子化学hyperchem6.01 ZIND0/1模拟计算结果显示,壳聚糖金属配合物高分子链上配位糖元对应的糖苷键比其他糖苷键更容易发生断裂,壳聚糖链断裂优先发生在该位置,降解反应具有更好的选择性和可控性。 相似文献
4.
5.
6.
7.
中性蛋白酶对壳聚糖的降解 总被引:14,自引:0,他引:14
用粘度测定法和还原糖测定法,研究了中性蛋白酶非专一性降解壳聚过程中温度,pH值,反应时间,酶浓度,底物浓度,金属离子及壳聚糖的脱乙酰度对中性蛋白酶降解壳聚糖反应速度的影响,确定了以壳聚糖为底物的中性蛋白酶的一些催化特性:最适温度为50℃;最适pH值为6.0;米氏常数Km值为1.1×10^-2g/mL;一定浓度的Cu62+,Ba^2+,Mn^2+抑制该酶的活性; 相似文献
8.
对壳聚糖进行液态均相络合反应制得壳聚糖铜配合物,IR、UV、元素分析及热重分析等检测证实了壳聚糖铜配合物中配位键的存在,且显示壳聚糖在形成配位结构后存在有利于降解的优势构象。以H2O2对壳聚糖-Cu(Ⅱ)络合物及壳聚糖进行氧化降解,考察降解过程中粘度的变化及降解产物分子量分布,在相同的降解条件下,壳聚糖铜配合物的降解速度明显高于壳聚糖,降解产物分子量分布较壳聚糖直接降解窄,结果进一步证明壳聚糖铜配合物中存在有利于降解的优势结构,同时证明以金属离子Cu(Ⅱ)对壳聚 相似文献
9.
壳聚糖在水溶液中的辐射降解反应 总被引:1,自引:0,他引:1
研究了壳聚糖在CH3COOH/NaCl缓冲溶液均相体系下的辐射降解反应,给出了H2O2、异丙醇、pH、样品初始分子量等因素对壳聚糖降解的影响,探讨了实验条件下溶液中不同自由基对壳聚糖降解的作用,并对辐照前后壳聚糖的结构进行了表征.结果表明,酸性条件下,壳聚糖的降解主要由.H和.OH自由基共同作用引起,加入H2O2或者通入N2O都能够略微提高.OH自由基浓度,对壳聚糖的降解有促进作用.加入异丙醇后,由于同时降低了.H和.OH自由基浓度,导致壳聚糖降解缓慢.当溶液的pH接近中性后,对壳聚糖的降解起主要作用的为.OH自由基,加入H2O2或者通入N2O都会增加.OH自由基的浓度,从而明显提高壳聚糖的降解速率.此外,研究发现低分子量的壳聚糖具有较快的降解速率.样品的UV、FTIR分析表明,辐照后除在壳聚糖分子链端生成羰基外,壳聚糖主链结构未见变化,脱乙酰度也没有显著改变,显示出辐射降解是一种有效的控制壳聚糖分子量方法. 相似文献
10.
11.
T. Naruephat D. Somsak V. Tharapong P. Amorn 《高分子科学》2006,(2):139-145
Depolymerization of poly(ethylene terephthalate) (PET) was performed in the tubular bomb microreactor which contained the solution of PET in methanol and dibutyltin oxide at the temperature ranging from 433 K to 473 K, the reaction time from 5 to 45 min and the catalyst-to-PET ratio of 0.3%-2% by weight. The optimal condition for PET depolymerization catalyzed by dibutyltin oxide is the temperature of 443-453 K, the reaction time of 20-25 min and 0.8% by weight of catalyst. By using differential methods, the activation energy for the depolymerization process was found to be 154.05 kJ/mol in the temperature range from 433-463 K. 相似文献
12.
壳聚糖浓溶液流变性质研究──分子量的依赖性 总被引:1,自引:0,他引:1
壳聚糖浓溶液流变性质研究──分子量的依赖性王伟,徐德时(中国科学院长春应用化学研究所高分子物理开放实验室长春130022)关键词壳聚糖,浓溶液,粘度,零剪切粘度,分子量作者曾研究了一些外部条件对壳聚糖浓溶液流变学性质的影响,如浓度、温度、溶剂性质、外... 相似文献
13.
14.
15.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-6):859-878
Thermotropic liquid crystalline terpolymers consisting of three units of p-oxybenzoate (B), ethylene terephthalate (E), and vanillate (V), were studied through a high-resolution thermogravimetry to ascertain their thermostability and kinetics parameters of thermal decomposition in nitrogen and air. Overall activation energy data of the major decomposition have been calculated through four calculating techniques. The thermal degradation occurs in three steps in nitrogen, but in four steps in air due to an additional thermo-oxidative step. The thermal degradation temperatures are higher than 436°C in nitrogen and 424°C in air and increase with increasing B-unit content at a fixed V-unit content of 5 mol%. The temperatures at the first maximum weight-loss rate are higher than 444°C in nitrogen and 431°C in air and increase slightly with an increase in B-unit content. The first, second, and third maximum weight-loss rates almost maintain at 10–11, 10–11, and 3.6–5.3%/min regardless of copolymer composition and testing atmosphere. The char yields at 500°C in both nitrogen and air are larger than 40 wt% and increases with increasing B-unit content. But the char yields at 800°C in nitrogen and air are quite different, i.e., 18–25 wt% in nitrogen and 0 wt% in air. The activation energy and Ln (pre-exponential factor) for the major decomposition are higher in nitrogen than in air and decrease slightly with an increase in B-unit content at a given V-unit content 5 mol%. There is no regular variation in the decomposition order with the variation of copolymer composition and testing atmosphere. It is found that the most V-unit-containing terpolymer exhibited the lowest degradation temperature, lowest activation energy, and lowest Ln (pre-exponential factor). The activation energy, decomposition order, and Ln (pre-exponential factor) of the thermal degradation for the terpolymers, are situated in the ranges of 121–248 kJ/mol, 1.5–2.8, 19–38 min?1, respectively. These results indicate that the terpolymers exhibit high thermostability. The isothermal decomposition kinetics of the terpolymer at 450°C have also been discussed and compared with the results obtained based non-isothermal high-resolution thermogravimetry. 相似文献
16.
甲基丙烯酸甲酯聚合动力学和分子量及分布的开放控制 总被引:1,自引:0,他引:1
在甲基丙烯酸甲酯聚合过程中 ,凝胶效应会导致转化率在短时间内出现突变 ,这对工业反应器非常危险 ,同时也导致分子量剧增、分子量分布加宽 .为了使聚合反应速度、分子量及分布同时得到控制 ,提出 3个控制目标 ,即热荷分布指数、预定分子量及变化、分子量分布指数 .在甲基丙烯酸甲酯半间歇聚合动力学和分子量模型的基础上 ,通过单体、溶剂和链转移剂 3种物料的流量和加料方式的仿真计算 ,对动力学、分子量及分布进行开放控制 ,并进行优化 ,得到热荷分布指数和分子量分布指数分别小于 2 0和 2 2的控制策略 ,且分子量达到预定要求 .选择两种优化策略进行实验验证 ,结果与开放控制仿真结果一致 相似文献
17.
INTRODUCTIONChitin is the second most naturally abundant biopolymer and is found in a variety of organisms, including fungalcell walls, the exoskeleton of crustaceans, skeletal tissue of mollusks and the integument of insects.When treated with alkali, chitin can be deactylated and turned into chitosan, which is a linear binaryheteropolysaccharide composed of (1-4) linked 2-acetamido-2-deoxy-β-D-glucopyranose and 2-amino-2-deoxy-β-D-glucopyranose residues. Chitosan has a wide variety of … 相似文献
18.
19.
Original chitosan with Mv of 2.7 × 105 was degraded by irradiation with γ-rays and a series of low molecular weight O-carboxymethylated chitosans (O-CMCh) were prepared based on the irradiated chitosan. A kinetic model of the irradiation of chitosan was put forward. Results show that the irradiation degradation of chitosan obeys the rule of random
degradation and the degree of deacetylation of irradiated chitosan is slightly raised. The antibacterial activity of O-CMCh is significantly influenced by its MW, and a suppositional antibacterial peak appears when Mv is equal to 2 × 105. 相似文献