过氧化氢在乙酸均相体系中对壳聚糖的降解

为制备分子量较低的可溶于水的壳低聚糖,研究了在乙酸均相体系中过氧化氢氧化降解壳聚糖的过程,采用凝胶渗透色谱法跟踪测定了壳聚糖氧化降解过程中分子量及其分布的变化,探索制备不同分子量壳低聚糖的适宜条件。     

臭氧降解法制备壳低聚糖及其结构表征

以85％脱乙酰度、相对分子质量为25×10^4的壳聚糖为原料,在20℃、pH为3、氧气流量0．7m^3／h的条件下降解6h,降解液用氨水调至pH为9,无沉淀,分别用截留相对分子质量为2k、3k、5k、10k的中空纤维膜超滤,获得所需聚合度的壳低聚糖。降解产物的结构用红外光谱、核磁共振碳谱表征,结果说明降解前后的结构基本没有变化。降解产物的聚合度用飞行时间质谱表征,其中经过2k中空纤维膜超滤后的壳低聚糖聚合度主要为4～10。     

固相载体法合成低聚糖

固相载体法合成低聚糖;固相载体;合成;低聚糖;偶联剂     

蒸发光散射检测器HPLC法测定大豆低聚糖

蒸发光散射检测器HPLC法测定大豆低聚糖;HPLC;ELS检测器;梯度洗脱;低聚糖;大豆     

高效液相色谱法测定果低聚糖中的糖含量

 以ＹＷＧ－ＮＨ２色谱柱和ＲＩＤ－６Ａ示差折光检测器对果低聚糖进行高效液相色谱法（ＨＰＬＣ）分析，获得了良好的分离效果。结果表明：果低聚糖糖浆中含有３０％～３５％的葡萄糖和５５％～５８％的果低聚糖（包括三糖、四糖和五糖），此外，还含有少量的果糖和蔗糖。ＨＰＬＣ能准确、快速地定性、定量果低聚糖中各组分糖，方法灵敏度高、重现性好，有理想的回收率，单糖和低聚糖的最低检出限在微克级。     

高效液相色谱法测定大豆乳清中大豆低聚糖

大豆低聚糖是大豆中可溶性糖质的总称,主要成分是蔗糖(双糖)、棉子糖(三糖)、水苏糖(四糖)等.大豆低聚精对人体具有奇特的生理功效,能有效地促进人体肠道内有益菌群双歧杆菌的增殖,并且具有整肠功能.测定大豆低聚糖的方法有高效液相色谱法和气相色谱法,这两种方法都具有定性、定量分析大豆低聚糖的优点.气相色谱法采用衍生化的方法测定,具有较高的灵敏度,但操作复杂,而且进样口的高温会使糖的衍生物分解,甚至可被留在进样口的残留物所催化.高效液相色谱法可以直接测定,不必采用衍生化处理,减少了糖的损失和偶然误差,具有前处理简单、分离效果好,回收率和重现性均比气相色谱法好的优点.本文采用高效液相色法测定大豆蛋白生产过程中排放大豆乳清中的大豆低聚糖,并对测定条件及测定效果进行了探讨.     

高效液相色谱法测定果低聚糖中的糖含量

以ＹＷＧ－ＮＨ２色谱柱和ＲＩＤ－６Ａ示差折光检测器对果低聚糖进行高效液相色谱法（ＨＰＬＣ）分析，获得了良好的分离效果。结果表明：果低聚糖糖浆中含有３０％～３５％的葡萄糖和５５％～５８％的果低聚糖（包括三糖、四糖和五糖），此外，还含有少量的果糖和蔗糖。ＨＰＬＣ能准确、快速地定性、定量果低聚糖中各组分糖，方法灵敏度高、重现性好，有理想的回收率，单糖和低聚糖的最低检出限在微克级     

甲壳低聚糖制备研究进展

壳聚糖/甲壳素;综述;甲壳低聚糖制备研究进展     

葡萄糖氧化酶-过氧化氢酶复合体系提纯异麦芽低聚糖

异麦芽低聚糖（IMO）具有低甜度、低热量、抗龋齿以及双歧因子特性等许多优异的生理功能。近年来,在医药保健、功能性食品和饲料添加剂等行业得到了广泛的应用。目前采用酶法生产的异麦芽低聚糖产品中异麦芽低聚糖的质量分数仅为50％左右,其中葡萄糖和麦芽糖的含量将近一半,     

双歧因子功能性低聚糖

功能性低聚糖作为双歧杆菌增殖因子的研究开发与应用越来越受到学者的关注,目前已证实具有特殊保健功能的低聚糖有低聚果糖、低聚异麦芽糖、低聚木糖、大豆低聚糖和低聚乳糖等。介绍了几种重要低聚糖的化学组成、特性、制法和应用等。     

Cu(Ⅱ)对壳聚糖的配位控制降解

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     

凝胶渗透色谱法研究壳聚糖生物材料酶降解过程的均匀性

壳聚糖是一种重要的生物医用材料,脱乙酰度是影响其生物降解性能的重要因素。运用凝胶渗透色谱研究了脱乙酰 度及相对分子质量分布相似、而聚合单元N-乙酰氨基-D-葡萄糖和D-氨基葡萄糖分布不同的两种壳聚糖材料在溶菌酶作用 下的降解过程,分析检测了壳聚糖材料在降解过程中的重均相对分子质量、相对分子质量多分散性和相对分子质量分布 的变化。发现聚合单元为随机分布的壳聚糖样品,其降解是均匀的;而聚合单元为段状分布的壳聚糖样品,其降解是非 均匀的;表明其聚合单元的分布方式决定壳聚糖材料酶降解过程的均匀性。     

Degradation of chitosan with self-resonating cavitation

For the degradation of chitosan, a novel physical method of self-resonating cavitation with strong cavitation effects was investigated in this paper. The effects of initial concentration, pH, temperature, inlet pressure and cavitation time on the degradation efficiency of chitosan were evaluated. It was found that the degradation efficiency was positively correlated with temperature and cavitation time, but was negatively correlated with the solution concentration. The degradation efficiency was maximized at pH of 4.4 and inlet pressure of 0.4 MPa. Under the experimental conditions, the intrinsic viscosity of chitosan solution was reduced by 92.2%, which was twice as high as the degradation efficiency where a Venturi tube cavitator was used. The viscosity-average molecular weights of initial and degraded chitosan were 651 and 104 kD, respectively. The deacetylation degree of chitosan slightly decreased from 89.34% to 88.05%. Structures and polydispersity of initial and degraded chitosan were measured by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), X-ray diffraction (XRD) and gel permeation chromatography (GPC). The results showed that the degradation process did not change the natural structure of chitosan. XRD peaks of the original chitosan were observed at 2θ of 9.59° and 20.00°, and the one at 2θ of 20.00° was obviously weakened after the degradation process, which indicated that the crystallinity of chitosan decreased significantly after the degradation. The polydispersity index of chitosan samples decreased from 3.17 to 2.75, indicating that the molecular-weight distribution of products after the degradation was more concentrated. The results proved that self-resonating cavitation prompted the degradation of chitosan and could reduce the polydispersity of the products for the production of oligochitosan with homogeneous molecular weights.     

Influence of molecular parameters on the degradation of chitosan by a commercial enzyme

The degradative activities of neutral protease against chitosan samples with different molecular parameters were characterized. The effects of the degree of deacetylation (DD) and molecular weight (MW) of chitosan on its susceptibility to degradation were investigated. The DD and MW of the chitosans were determined using potentiometric titration and viscometry, respectively. The molecular weight distribution of initial and degraded commercial chitosan was investigated by gel permeation chromatography. Initial degradation rates (r) were determined from the plots of viscosity decrease against time of degradation. The time courses of degradation of chitosans with neutral protease were non-linear and the enzymatic hydrolysis was an endo-action. Classical Michaelis-Menten kinetic parameters were measured by analyzing the amount of reducing sugars and Eadie-Hofstee plots established that hydrolysis of chitosan by neutral protease obeyed Michaelis-Menten kinetics. Michaelis-Menten parameters and initial degradation rates were calculated and compared to determine the influences of DD and MW on hydrolysis. The results showed that higher DD and higher MW chitosans possessed a lower affinity for the enzyme and a slower degradation rate. Those samples with a lower DD and lower MW were more susceptible substrates.     

壳聚糖超声可控降解及降解动力学研究

通过正交实验法考察了壳聚糖溶液浓度、反应温度、超声强度以及醋酸溶液浓度对超声降解反应的影响,确定了最佳反应条件,制备了一系列不同分子量的壳聚糖.研究了壳聚糖溶液浓度、反应温度以及壳聚糖原料分子参数与降解速率常数的关系.通过红外光谱、X-射线衍射和凝胶渗透色谱对降解产物进行了表征.结果表明,超声降解壳聚糖的最佳条件为10℃,壳聚糖溶液浓度2.5g/L.降解速率常数随壳聚糖溶液浓度和反应温度的降低而增大.高分子量和低脱乙酰度的壳聚糖原料有较高的降解速率和降解速率常数,壳聚糖原料的分子量对降解速率和降解速率常数的影响大于脱乙酰度对其的影响.超声波导致了壳聚糖分子量的降低和产物晶体结构的破坏,但没有改变产物的脱乙酰度和糖残基结构.     

用GPC研究壳聚糖氧化降解过程中的分子量及其分布

用凝胶渗透色谱法跟踪研究了过氧化氢对壳聚糖氧化降解过程中壳聚糖的分子量及其分布的影响,结果表明,反应温度、时间和过氧化氢用量对壳聚糖的降解程度及降解产品质量均有影响。     

Synthesis of green CdSe/chitosan quantum dots using a polymer-assisted γ-radiation route

Chitosan-coated CdSe quantum dots (CdSe/CS QDs) were successfully synthesized in aqueous system through a γ-radiation route at room temperature under ambient pressure. The diameter of the resulting QDs was about 4 nm with narrow size distribution. The synthesized QDs exhibited an absorption peak at 460 nm and an emission peak at 535 nm. These QDs were cubic zinc blende CdSe in core structure and coated with chitosan on surface, with fine solubility in water.     

壳聚糖─海藻酸钠微囊对蛋白质控制释放的研究

采用乳化法制备了可注射用壳聚糖海藻酸钠微囊, 其粒径小于２００ μｍ ,且具有相对较窄的近似高斯分布。牛血清白蛋白作为模型药物在微囊中的包埋率可超过５０ ％ 。通过壳聚糖在海藻酸钠微囊表面的复合,牛血清白蛋白从微囊中的持续释放时间从几个小时延长到半个月以上。     

Synergetic degradation of chitosan with gamma radiation and hydrogen peroxide

Chitosan samples were irradiated by ⁶⁰Co γ-rays in the presence of hydrogen peroxide with radiation dose from 10 kGy to 100 kGy. The degradation was monitored by gel permeation chromatography (GPC), revealing the existence of a synergetic effect on the degradation. Structures of the degraded products were characterized with Fourier-transform infrared spectra (FT-IR), ultraviolet-visible spectral (UV-vis) analysis, and X-ray diffraction (XRD). Results showed that the crystallinity of chitosan decreases with degradation, and the crystalline state of water-soluble chitosan is entirely different from that of water-insoluble chitosan. An elemental analysis method was employed to investigate changes in the element content of chitosan after degradation. Mechanism of chitosan radiation degradation with and without hydrogen peroxide was also discussed.