Inhibition of lipase from rice (Oryza sativa) by diethyl-p-nitrophenyl phosphate

The inhibition of rice bran lipase (RBL) by diethyl-p-nitrophenyl phosphate was studied with reference to kinetics, nature of inhibition and also elucidate the effect of the inhibitor on the structure—function of the enzyme. Enzyme activity measurements shows that the inhibitor is more effective at 0.050 mM concentration of diethyl-p-nitrophenyl phosphate and the activity is 50% at this level of inhibitor concentration. The affinity of substrate for the enzyme was observed by the increase in the velocity of the reaction with increase in the substrate concentrations and double reciprocal plot indicates that the inhibition followed a competitive in nature and inhibition constant K _i is found to be 0.016 mM at pH 7.0. The decrease in apparent thermal denaturation temperature to 4 °C compared to control indicates the destabilization of enzyme in the presence of inhibitor. Fluorescence spectral measurements suggests that pronounced quenching of fluorescence intensity of RBL occurs at higher concentrations of diethyl-p-nitrophenyl phosphate and ‘K _a’ value was found to be 2.4 × 10⁴ M⁻¹ with free energy change ΔG^o—26 kJ/mol at 30 °C suggesting strong binding between the enzyme and the inhibitor with microenvironmental changes occur at the active site or in the neighbourhood of active site. The far UV-CD data suggest that there is no significant changes in the conformation of the enzyme as a result of binding of diethyl-p-nitrophenyl phosphate. These results indicate that diethyl-p-nitrophenyl phosphate is a inhibitor of RBL and binds to the enzyme in brining about inhibition without any structural alterations.     

草珊瑚多糖对经脂多糖刺激的RAW264.7巨噬细胞的免疫调节作用研究

为研究草珊瑚多糖对RAW264.7巨噬细胞的免疫调节作用,建立LPS刺激的RAW264.7细胞模型,通过MTT法测定,观察草珊瑚多糖对RAW264.7细胞增殖影响并评价细胞毒性。同时,对草珊瑚多糖抑制模型细胞炎症因子一氧化氮(NO)表达及吞噬活性进行研究。结果表明,草珊瑚多糖可显著抑制RAW264.7细胞增殖水平,其细胞毒性分级为1级或以下。同时,草珊瑚多糖可显著抑制模型细胞NO表达及巨噬细胞吞噬活性。此研究将为深入研究草珊瑚抗炎活性作用机制及草珊瑚资源开发提供理论依据。     

Immobilization of lipase on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) hydrogel for the synthesis of butyl oleate

Lipase from Candida rugosa was immobilized by entrapment on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) [poly(VP-co-HEMA)] hydrogel, cross-linked with ethylene glycol dimethacrylate (EDMA). The immobilized enzyme was used in the esterification of oleic acid with butanol in hexane. The activities of the immobilized enzyme preparations and the leaching of the enzyme from the hydrogel supports with respect to composition were investigated. The thermal, solvent, and storage stability of the immobilized preparations also were determined. Increasing the percentage VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized onto VP(%):HEMA(%), 90:10 hydrogel had the highest activity. Increasing the hydrophobicity of the hydrogel (increasing the percentage HEMA) seemed to decrease leaching of the enzyme from the support. Immobilized lipase on 100% HEMA hydrogel indicated highest entrapment and lowest leaching by hexane washing. The lipase immobilized on VP(%):HEMA(%), 50:50 hydrogel showed highest thermal, solvent, and storage stability compared to lipase immobilized on other hydrogel compositions as well as the native lipase.     

马来酸酐－醋酸异丙酯二元固液平衡的测定和关联

马来酸酐－醋酸异丙酯二元固液平衡的测定和关联陈新志侯虞钧（浙江大学化工系，杭州３１００２７）关键词固液平衡活度系数１引言相平衡数据在化工生产和研究中占有重要的地位。流体相平衡已得到了广泛的研究，并积累了大量的数据，与之相应的实验方法也较为完善，同时...     

Activity,selectivity, and methanol tolerance of novel carbon-supported Pt and Pt<Subscript>3</Subscript>Me (Me = Ni,Co) cathode catalysts

The activity, selectivity, and methanol tolerance of novel, carbon supported high-metal loading (40 wt.%) Pt/C and Pt₃Me/C (Me = Ni, Co) catalysts for the O₂ reduction reaction (ORR) were evaluated in model studies under defined mass transport and diffusion conditions, by rotating (ring) disk and by differential electrochemical mass spectrometry. The catalysts were synthesized by the organometallic route, via deposition of pre-formed Pt and Pt₃Me pre-cursors followed by their decomposition into metal nanoparticles. Characteristic properties such as particle sizes, particle composition and phase formation, and active surface area, were determined by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. For comparison, commercial Pt/C catalysts (20 and 40 wt.%, E-Tek, Somerset, NJ, USA) were investigated as well, allowing to evaluate Pt loading effects and, by comparison with the pre-cursor-based catalyst with their much smaller particle sizes (1.7 nm diameter), also particle size effects. Kinetic parameters for the ORR were evaluated; the ORR activities of the bimetallic catalysts and of the synthesized Pt/C catalyst were comparable and similar to that of the high-loading commercial Pt/C catalyst; at typical cathode operation potentials H₂O₂ formation is negligible for the synthesized catalysts. Due to their lower methanol oxidation activity the bimetallic catalysts show an improved methanol tolerance compared to the commercial Pt/C catalysts. The results indicate that the use of very small particle sizes is a possible way to achieve reasonably good ORR activities at an improved methanol tolerance at DMFC cathode relevant conditions.     

Measurement of Activity Coefficients from Unsteady State Evaporation and Growth of Microdroplets

Techniques are presented for determination of activity coefficients of binary systems from unsteady state evaporation and growth of single microdroplets in controlled environments. A high-precision light scattering method based on resonances observed in light scattering by microdroplets was used to determine the size and composition of a microdroplet as functions of time. The techniques were validated through data on growth of glycerol microdroplets in slowly developing water vapor concentration fields and evaporation of microdroplets, containing volatile dimethylphthalate (DMP) and nonvolatile dioctylphthalate (DOP), in vapor-free atmospheres. When the water vapor concentration in the surrounding gas changes slowly a glycerol droplet maintains a dynamic equilibrium with the water vapor; thus the activity coefficient of water was determined from knowledge of the droplet composition and the water vapor saturation ratio in the gas phase. The activity coefficients of DMP were determined on the basis that the instantaneous evaporation rate of a DMP-DOP microdroplet in a vapor-free atmosphere is equal to the product of the activity of DMP and the evaporation rate of a pure DMP droplet. The activity coefficient values obtained from microdroplet experiments are highly reproducible and agree with data available in the literature.     

失落的城市公共空间--被遗忘了的人行步道

针对当前城市人行步道使用率极低的问题,提出了必要性活动、自发性活动、社会性活动三个概念,由此分析其失落的原因,并就此提出了改造目标及改造方案.     

绿色马峦山 生态健康游——马峦山郊野公园规划设计

郊野公园是指位于城市郊区、以自然风光为主要内容,满足居民周末出行游憩康乐活动需要的公园。深圳市马峦山郊野公园规划,对郊野公园的生态保护与游憩开发两方面进行了探索性思考,针对二者对立统一的关系,通过规划理念的创新探索、生物多样性调查与研究和景观资源评析,提出郊野公园总体布局、游憩活动策划以及生物多样性保护规划,介绍并阐述了如何在保护的前提下,为市民提供更广泛、更多样的亲近自然的游憩方式,以及确定生态保护与修复的重点。     

基于老年人行为特点的养老机构公共活动空间设计研究

本文以养老机构中非特定功能的 公共活动空间为研究对象,通过对北京市两 所特大型养老机构中分散式公共空间与集中 式公共空间利用实态的比较分析,明确自理、 介助、介护老人的行为特点。并从公共空间 的物理环境、位置、空间形态与尺度、与居室 的距离等方面,分析公共空间使用时的影响 要素,明确使用者的空间需求。在此基础上, 提出养老机构公共空间设计的建议     

街道空间对老年人日常活动的影响初探

老年人日常活动机会与其健康水平息 息相关。街道作为居民日常活动的空间载体,对 其活动能力的提升意义重大。为明晰老年人日常 活动的街道环境影响因子,提高活动出行质量, 从可行能力视角切入,将老年人日常感知的活动 机会作为因变量,街道可步行性（街道连通性、 街廓尺度、步行安全性）、生活性（设施密度及 丰富度、设施可达性）以及美学性（街道绿化、 界面连续性）三个维度特征数据作为自变量,运 用多元线性回归分析,揭示街道环境要素对活 动能力水平的作用效应及影响机制。研究发现, 不同维度街道环境要素对不同类型活动能力差 异显著,对比街道美学性环境要素,街道可步行 性、生活性要素是影响老年人活动能力的主导方 面。其中,在步行性维度,停车方式对活动能力 至关重要,整合度次之;在生活性维度,商业设 施可达性对活动能力的影响十分关键,设施种类次之,此外设施数量与休闲和医疗设施可达性对 活动能力的作用效应也不容忽视。据此,为提高老年人活动水平,选取两个典型案例提出针对性 的街道环境优化建议。