排序方式: 共有53条查询结果,搜索用时 15 毫秒
51.
52.
53.
Dr. Jian‐zhi Wang Dr. Guang‐hui Zhao Dr. Yan‐feng Li Xiao‐meng Peng Yan‐tao Li 《化学:亚洲杂志》2013,8(12):3116-3122
Based on the characteristics of polycations of chitosan and glucoamylase, which are oppositely charged, they were successfully alternatingly deposited onto the surface of aldehyde‐modified Fe3O4 nanoparticles by using a layer‐by‐layer ion exchange method to form magnetic carriers to construct multilayer films (designated as Fe3O4@(CS/GA)n). The (CS/GA)n film systems were endowed with the pH‐dependent properties of chitosan as well as the catalytic activity of glucoamylase. The changes in weight loss and surface chemistry, morphology, and magnetic sensitivity were monitored and verified by UV/Vis spectroscopy, zeta potential, TEM, and a vibrating sample magnetometer. Subsequently, the influence of the number of bilayers, storage stability, pH, temperature, and reusability of Fe3O4@(CS/GA)5 biocatalysts on catalytic activity were investigated. The results from characterization and determination remarkably indicate that Fe3O4@(CS/GA)5 presents excellent catalytic activity, storage stability, pH stability, and reusability in comparison with free enzyme. Fe3O4@(CS/GA)5 retained >60 % of its initial activity at 65 °C over 6 h; the optimum temperature and pH also increased to the ranges of 45–65 °C and 2.5–3.5, respectively, and only 27 % activity was lost after 10 cycles. This new strategy simplifies the reaction protocol and improves encapsulation efficiency and catalytic activity for new potential applications in biotechnology. 相似文献