A theoretical approach to some analytical properties of heterogeneous enzymatic assays

Heterogeneous enzymatic assays (HEA), where an enzyme in solution acts upon an immobilized substrate, are been increasingly used. Given their high throughput and versatility they hold great potential for developing massive enzyme inhibitor screening. However, current HEA lack, in general, rigorous quantitative use. This is in part due to technical problems as a multiplicity of suboptimal substrate populations achieved with traditional immobilization techniques but, more importantly, is due to a poor understanding of the particular kinetic behavior of these systems. This paper addresses the kinetic features of HEA that arise from the very low amount of solid-phase substrate and the resulting inalterability of the free enzyme concentration during the assay, which classify HEA as enzyme quasi-saturable systems (EQSS). We assessed the optimal enzyme concentration working range and time of reaction. We also considered certain attributes of HEA for evaluating isosteric inhibitors. These studies were done on the basis of a simplified model for the kinetics of EQSS and a formal splitting of the functional factor of the analytical sensitivity of an enzymatic assay into [E(o)]/K(m)-dependent and temporal components.     

Correlation of analyte structures with biosensor responses using the detection of phenolic estrogens as a model

The apparent increase in hormone-induced cancers and disorders of the reproductive tract in wildlife and humans has led to a search for an accurate and reliable method for monitoring endocrine-disrupting chemicals (EDCs). This study presents a generic approach that may allow researchers to establish screening procedures for potential EDCs by correlating the analyte structures with biosensor responses and explain possible reaction mechanisms. A simple amperometric tyrosinase-based biosensor (Tyr-CPE) has been developed for the detection of phenolic EDCs. The investigation of the enzymatic oxidation of selected phenolic estrogens was first carried out using UV-vis spectroscopy. The result was used to correlate sensor responses to enzymatic activity. Natural phytoestrogen polyphenols, including resveratrol (RES), genistein (GEN), and quercetin (QRC), were compared with synthetic estrogens, for example, bisphenol A (BPhA), nonylphenol (NPh), and diethylstilbestrol (DES). The Tyr-CPE biosensor resulted in rapid, simple, and accurate measurement of phenolic estrogens with varying degrees of sensitivity, selectivity, and response times. The sensor responses have been evaluated for the detection of binary and tertiary mixtures of EDCs and natural estrogens. The results showed that BPhA could be successfully discriminated in a composite mixture containing NPh and DES at various ratios. In the case of natural phenolic estrogens GEN, RES, and QRC, the sensor allows the determination of a total phenolic content. The sensor was also validated for the detection of BPhA in a real environmental water sample, and the results was compared with standard ASTM method 9065. Mechanistically, our results indicated that the number of OH groups, the nature and the position of aryl ring substituents, or both could affect the detection limit and the biosensor sensitivity.     

Comparative study of effects of diet therapy including eiconol or linseed oil on several parameters of lipid metabolism in patients with type 2 diabetes mellitus

It was investigated the influence of a diet supplemented with polyunsaturated fatty acids (PUFA) omega-3 on dynamic of basal glycaemia, lipid profile and composition of fatty acids of erythrocytes in type 2 diabetic patients. Traditional 9 diet was supplemented with fish ("Eiconol", 8 grams per day) or vegetable (linseed oil, 17.5 grams per day) PUFA omega-3. The results investigations indicated that a omega-3 PUFA-enriched diet has a beneficial effects on lipid metabolism. But dietary administration of PUFA omega-3 may be used differently for correction of dislipoproteinemia in diabetic patients.     

框格式地下连续墙在桐子林水电站中的应用

桐子林水电站导流明渠布置在右岸滩地上,明渠底板和左导墙基础为粉砂质粘土,属软弱基础,为满足结构要求,设计提出对该地层采用框格式连续墙进行基础处理.经过方案比选,"十"字形节点部位采用桩结构形式成槽施工,钢筋混凝土接头采用起拔导管与投放粘土袋相结合的施工方案,从施工效果和质量情况来看,所选方案符合框格式地下连续墙施工的特点,完全能满足工程的要求.     

数字视频广播系统概述

今天 ,尽管我们在家里收看的仍然是模拟电视节目 ,但是当你通过卫星电视网、有线电视网或开路电视网观看电视节目时 ,你已经位于电视数字传输的最后一个环节 ,它正在经历着一场数字化革命 ,以达到电视节目的全数字化传输。在电视数字化的进程中 ,国际组织ＤＶＢ(ＤｉｇｉｔａｌＶｉｄｅｏＢｒｏａｄｃａｓｔｉｎｇ)提出了全套的解决方案 :数字卫星电视 (ＤＶＢ -Ｓ)、数字有线电视 (ＤＶＢ -Ｃ)、数字开路电视 (ＤＶＢ -Ｔ) ,这意味着电视节目数字化的时代已经到来 !在欧洲 ,从 1991年开始 ,电视台、家电产品生产厂家和标准制订者坐到一起 ,…     

遂宁白禅寺电航工程围堰防渗质量浅析

白禅寺电航工程临时围堰由两期组成，围堰防渗采用高喷灌浆和静压灌浆相结合，两期围堰闭气效果差，漏水比较大，从地质、设计、施工几方面对围堰防渗质量进行分析，目的是为以后类似工程提供经验。     

Delayed effects of chronic low-dose high linear energy transfer (LET) radiation on mice in vivo

In the present work, the delayed effects of chronic high linear energy transfer (LET) radiation in polychromatic erythrocytes (PCEs) of mice bone marrow were investigated in vivo. Irradiation of the two-month-old SHK white mongrel random-bred male mice was performed in the radiation field behind the concrete shield of the accelerator of 70 GeV protons to accumulate doses of 0.005-0.16 Gy. The dependence of the biological response on dose, adaptive response (AR) and genomic instability (GI) in F(1) and F(2) generations from males irradiated with doses of 0.005 and 0.16 Gy and from males exposed to combined action of immunomodulator-bendazol hydrochloride (BH) and of 0.16 Gy irradiation, were examined using the micronucleus formation test. The data demonstrated that irradiation of mice with these doses lead to an increase in the level of cytogenetic damage and induces no AR. With analysis of the bone marrow radiosensitivity to 1.5 Gy of X rays and the capacity to AR it was found that the chronic high-LET irradiation of parents induced the GI at least two generations. The combined exposure to BH and the dose of 0.16 Gy induces no AR in F(0) generation but induces AR in F(1) and F(2) offspring.     

H2AX phosphorylation in response to DNA double-strand break formation during bystander signalling: effect of microRNA knockdown

Upon DNA double-strand break (DSB) formation, hundreds of H2AX molecules in the chromatin flanking the break site are phosphorylated on serine residue 139, termed gamma-H2AX, so that virtually every DSB site in a nucleus can be visualised within 10 min of its formation using an antibody to gamma-H2AX. One application of this sensitive assay is to examine the induction of DNA double-strand damage in subtle non-targeted cellular effects such as the bystander effect. Here whether microRNA (miRNA) serve as a primary signalling mechanism for bystander effect propagation by comparing matched human colon carcinoma cell lines with wild-type or depleted levels of mature miRNAs was investigated. No major differences were found in the levels of induced gamma-H2AX foci in the tested cell lines, indicating that though miRNAs play a role in bystander effect manifestation, they appear not to be the primary bystander signalling molecules in the formation of bystander effect-induced DSBs.