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931.
932.
933.
934.
Esterases and lipases can process amphiphilic esters used as drugs and prodrugs and impact their pharmacokinetics and biodistribution. These hydrolases can also process ester components of drug delivery systems (DDSs), thus triggering DDSs destabilization with premature cargo release. In this study we tested and optimized assays that allowed us to quantify and compare individual esterase contributions to the degradation of substrates of increased lipophilicity and to establish limitations in terms of substrates that can be processed by a specific esterase/lipase. We have studied the impact of carbonic anhydrase; phospholipases A1, A2, C and D; lipoprotein lipase; and standard lipase on the hydrolysis of 4-nitrophenyl acetate, 4-nitrophenyl palmitate, DGGR and POPC liposomes, drawing structure–property relationships. We found that the enzymatic activity of these proteins was highly dependent on the lipophilicity of the substrate used to assess them, as expected. The activity observed for classical esterases was diminished when lipophilicity of the substrate increased, while activity observed for lipases generally increased, following the interfacial activation model, and was highly dependent on the type of lipase and its structure. The assays developed allowed us to determine the most sensitive methods for quantifying enzymatic activity against substrates of particular types and lipophilicity. 相似文献
935.
936.
聚酯粉末涂料配方组成与性能研究 总被引:2,自引:0,他引:2
研究了不同厂家出产的聚酯树脂,不同固化剂及其不同用量,不同助剂、颜料品种和填料品种对聚酯粉末涂料及其涂膜性能的影响。结果表明,使用不同厂家生产的聚酯树脂所得的粉末涂料的胶化时间和熔融流动性不同;粉末的性能与固化体系有关;固化剂的用量对涂膜性能有较大的影响;流平剂的质量分数以不超过1.5%为宜;配方的设计应按用户要求,选择适宜的颜、填料品种及其用量。 相似文献
937.
938.
介绍了用于简化化学反应动力模型的计算奇异值摄动方法(CSP),给出了其基本思想与具体计算方法,然后用该方法来对一氧化碳/氢气在空气中燃烧的化学反应、激波管中甲烷的点火燃烧反应实例进行了简化。从计算结果看,CSP方法是一种比较有效的化学反应模型简化方法,用该方法简化得出的简化模型不仅减少了微分求解的组分数目,而且保持了较高的计算精度,能有效提高计算效率,具有较强的工程实际价值。 相似文献
939.
Sergey Nickolayevich Mensov Gleb A. Abakumov Maxim V. Arsenyev Maxim A. Baten'kin Sergey A. Chesnokov Alexey N. Konev Yuri V. Polushtaytsev Margarita P. Shurygina Maria Yu. Zakharina 《应用聚合物科学杂志》2020,137(34):48976
The process of two-wave photopolymerization of a UV-curable composition with an optically degrading inhibitor is considered. By numerical simulation, it is shown that in the composition layer uniformly exposed to UV-radiation, such systems allow getting segments with different conversion under the action of inhomogeneous visible light. Based on the data on the photopolymerization kinetics of the compositions from triethylene glycol dimethacrylate (TEGDMA) and bisphenol-A glycidyl dimethacrylate (bis-GMA) with the UV-initiator 2,2-dimethoxy-2-phenylacetophenone (DMPA), it was shown that 3,5-di-tert-butyl-o-benzoquinone (35Q) with N,N-dimethylaniline (DMA, “Aldrich”, 99%) can serve as an inhibitor that degrades under action of visible radiation. Combining inhomogeneous visible light generated with a conventional DLP-projector and uniform UV-radiation of LED (365 nm) the two-wave lithographic process was implemented to create polymeric 2D-structures in 20 μm layer of the compositions from TEGDMA (70)/bis-GMA (30)/DMPA (0.05 wt%)/35Q (0.5 wt%)/DMA (1 wt%). 相似文献
940.
ABSTRACT The solid residue of the cold press oil extraction from prickly pear (Opuntia ficus indica L.) fruit seeds was evaluated as a low-cost biosorbent for biosorption of Cr(VI) from aqueous solutions. Batch experiments were conducted as a function of initial pH, contact time, biosorbent dose, initial Cr(VI) concentration, and temperature. Biosorption was highly pH-dependent and found to be maximum at pH 1.0. Langmuir and Freundlich equations fitted very well with experimental data. The maximum monolayer adsorption capacity was 19.61 mg/g at 298 K and pH 1.0. Biosorption kinetics was controlled by the pseudo-second-order model. Thermodynamic parameters indicated that biosorption of Cr(VI) was a spontaneous, favorable and endothermic process. The activation energy was found to be 40.68 kJ.mol?1. 相似文献