植物体系中甲酯酶的底物专一性的理论研究

酶对天然底物的高度专一性是酶的特点之一. 然而关于酶是如何对底物具有高度专一性以及识别能力, 我们的理解仍然缺乏. 本文以植物体系中发现的一组甲酯酶(MESs)对一些底物[包括水杨酸甲酯(MeSA), 茉莉酮酸甲酯(MeJA)和吲哚-3-乙酸甲酯(MeIAA)]的催化反应为例, 报道了同源建模和理论计算对茉莉酮酸甲酯酶(AtMES10)和水杨酸结合蛋白2(SABP2)的研究结果. 基于简单的锁-钥匙理论(底物与酶结合时不发生基团的碰撞或严重排斥), 以底物对接到酶的活性部位(即底物中—COO的一部分占据可被催化丝氨酸亲核进攻的位置) 为原则, 可以在空间上为酶对底物的专一性提供解释. 模拟结果表明, SABP2可对MeSA有高活性, 对MeJA和MeIAA有低或无活性; AtMES10可对MeJA有高活性, 而对MeSA和MeIAA有低或无活性, 这与实验结果相一致. 因此, 相关酶的结构预测与计算机模拟对了解酶的底物专一性具有重要的意义.     

头发铅含量测定的应用价值评价

调查了125例2－5岁儿童铅中毒状况，测定其全血铅含量和头发铅含量，以全血铅含量为标准，应用诊断试验评价方法评价头发铅测定的应用价值。结果表明，该试验的灵敏度可达88．3％，应用串联试验，即同时测定头发中锌、铁、钙含量，可将该试验的特异度提高至81．8％，阳性预测值达69．6％，阴性预测值达78．8％。     

电磁轴承系统的刚度阻尼特性分析

分析了电磁轴承系统的刚度阻尼特性与系统结构参数及其控制器频响特性之间的关系。给出了系统控制电流的相位对系统稳定性和刚度阻尼特性的影响。提出了电磁轴承系统的复阻尼概念，以及部分刚度阻尼特性指标的实际意义和计算方法。     

ELIHKSIR Web Server: Evolutionary Links Inferred for Histidine Kinase Sensors Interacting with Response Regulators

Two-component systems (TCS) are signaling machinery that consist of a histidine kinases (HK) and response regulator (RR). When an environmental change is detected, the HK phosphorylates its cognate response regulator (RR). While cognate interactions were considered orthogonal, experimental evidence shows the prevalence of crosstalk interactions between non-cognate HK–RR pairs. Currently, crosstalk interactions have been demonstrated for TCS proteins in a limited number of organisms. By providing specificity predictions across entire TCS networks for a large variety of organisms, the ELIHKSIR web server assists users in identifying interactions for TCS proteins and their mutants. To generate specificity scores, a global probabilistic model was used to identify interfacial couplings and local fields from sequence information. These couplings and local fields were then used to construct Hamiltonian scores for positions with encoded specificity, resulting in the specificity score. These methods were applied to 6676 organisms available on the ELIHKSIR web server. Due to the ability to mutate proteins and display the resulting network changes, there are nearly endless combinations of TCS networks to analyze using ELIHKSIR. The functionality of ELIHKSIR allows users to perform a variety of TCS network analyses and visualizations to support TCS research efforts.     

米托蒽醌与B-DNA相互作用的分子模拟

针对嵌插型抗癌药物米托蒽醌(mitoxantrone,MTX)同B-DNA间作用模式的争议,采用分子模拟方法研究了米托蒽醌分子与B-DNA分子的相互作用.结果表明:米托蒽醌分子插入到B-DNA中有大小沟选择性及碱基对特异性,更倾向从小沟方向插入到DNA分子中;对5'-CG碱基对有特异性识别.通过详细能量项的分析,揭示了米托蒽醌插入DNA分子的驱动力及对碱基的特异性识别作用主要是空间相互作用特别是静电相互作用.在最佳作用位点复合物的构象分析则表明蒽醌环只有一部分插入碱基对中,侧链在小沟中延磷酸基骨架以3'-5'方向伸展,并通过静电作用进一步增强米托蒽醌与B-DNA的结合.     

LC-MS在体内药物分析方法学研究中常见的问题及其对策

液相色谱-质谱联用技术(liquid chromatography-mass spectrometry,LC-MS)已成为体内药物分析及其相关研究领域中不可或缺的工具.虽然该技术具有高选择性、高灵敏度以及高通量等特点,但在体内药物分析方法学研究中,仍然会面临诸如待测物需衍生化、复方制剂体内多组分同时测定时高浓度组分的质谱响应饱和、方法专属性误判、基质效应、残留效应等一系列挑战和问题,本文综述了这些常见问题的相应对策.     

Effect of oligonucleotide probes substituted by deoxyinosines on the specificity of SNP detection on the DNA microarray

One of the main factors that can affect the quality of microarray results is the microarray hybridization specificity. The key factor that affects hybridization specificity is the design of the probes. In this paper, we described a novel oligonucleotide probe containing deoxyinosines aimed at improving DNA hybridization specificity. We compared different probes to determine the distance between deoxyinosine base and SNPs site and the number of deoxyinosine bases. The new probe sequences contained two set of deoxyinosines (each set had two deoxyinosines), in which the interval between SNP site and each set of deoxyinosines was two bases. The new probes could obtain the highest hybridization specificity. The experimental results showed that probes containing deoxyinosines hybridized effectively to the perfectly matched target and improved the hybridization specificity of DNA microarray. By including a simple washing step after hybridization, these probes could distinguish matched targets from single‐base‐mismatched sequences perfectly. For the probes containing deoxyinosines, the fluorescence intensity of a match sequence was more than eight times stronger than that of a mismatch. However, the intensity ratio was only 1.3 times or less for the probes without deoxyinosines. Finally, using hybridization of the PCR product microarrays, we successfully genotyped SNP of 140 samples using these new labeled probes. Our results show that this is a useful new strategy for modifying oligonucleotide probes for use in DNA microarray analysis.     

Mode Specificity,Bond Selectivity,and Product Energy Disposal in X + CH4/CHD3 (X=H,F, O(3P), Cl,and OH) Hydrogen Abstraction Reactions: Perspective from Sudden Vector Projection Model

Reactions between methane and various radicals have become the workhorse in our understanding of mode specificity and bond selectivity in bimolecular reactions. In this work, the recently proposed Sudden Vector Projection (SVP) model is used to gain insight into the existing experimental and theoretical data on these reactions. The SVP model attributes mode specificity and bond selectivity to the coupling of reactant modes/bonds with the reaction coordinate at the transition state. In the sudden limit, the strength of the coupling can be simply computed by projecting the corresponding reactant normal mode vector onto that of the imaginary frequency mode at the saddle point. In addition, the SVP model can be used to predict energy disposal in the products, thanks to microscopic reversibility. It is shown that most of the mode‐specific and bond‐selective chemistry in X + CH₄/CHD₃ (X=H, F, O(³P), Cl, and OH) reactions can be reasonably understood with this simple model.     

Solid phase analytical derivatization of anthropogenic and natural phenolic estrogen mimics with pentafluoropyridine for gas chromatography-mass spectrometry

A simple, low cost, fast and sensitive method is reported for the determination of the four endocrine disrupting chemicals (EDCs) 4-tert-butylphenol, 4-tert-octylphenol, bisphenol A and 17β-estradiol using pentafluoropyridine as the derivatizing reagent. These EDCs were determined by simultaneous extraction and derivatization in a solid phase analytical derivatization (SPAD) technique without the aid of any phase transfer catalyst (PTC) or an ion-pair mechanism. Recoveries of analytes as their tetrafluoropyridyl derivatives from water ranged from 71% for 4-tert-butylphenol to 106% for 17β-estradiol; from urine they ranged from 61% for 17β-estradiol to 91% for 4-tert-octylphenol; and from humic acids solution the ranged from 59% for 17β-estradiol to 104% for 4-tert-octylphenol in humic acid solutions. Calibration curves were constructed from a matrix of human male urine in the range 1-40 ng/mL and had coefficients of correlation greater than 0.99. For 4-tert-butylphenol, bisphenol A and 17β-estradiol the limits of quantitation were 5 ng/mL and for 4-tert-octylphenol it was 1 ng/mL. This method was applied to determine EDCs and detected 4-tert-octylphenol, bisphenol A and 17β-estradiol in concentrations comparable to those found in the literature. The method offers advantages in speed of analysis, reduced reagent and specificity of derivatization.