亚硝酸甲酯分子在440nm附近的激光光解

近年来亚硝酸甲酯分子（CHa0NO）的光解动力学研究十分活跃｛‘5］，主要集中在紫外激光的单光子解离的机理，光解过程的矢量相关性质和光解产物的态分布．CH30NO分子的解离能D。（CH30－NO）＝174kJ·mol‘，若单从能量上看，人＜689。的光就能使其解离，但人＞400urn的光解离研究还未见报导．＊H30＊0分子在人＞40onm的强激光场下是充电离还是先解离，是单光子解离还是多光子解离，以及通过哪个电子态解离都不清楚．时间飞行质谱不仅具有质量分辨率高、范围宽，而且响应快，因此适合做光解光电离过程初生态产物的探测．特别是时间飞…     

离聚体的结构表征——Ⅴ.含氟离聚体中离子微区稳定性的研究

本文用DSC方法研究了羟酸型含氟离聚体中不同金属离子种类、可离子化基团含量、配位结构单元构型及离子微区大小对离聚体中离子微区稳定性的影响。实验表明:离聚体中金属离子配位能力愈强,羟酸含量愈高,离子微区尺寸愈大,则相应离聚体中离子微区稳定性愈大。铅高聚体>锌离聚体>钙离聚体>钠离聚体。     

Dynamical Aspects of TEM-1 β-Lactamase Probed by Molecular Dynamics

The dynamical aspects of the fully hydrated TEM-1 β-lactamase have been determined by a 5 ns Molecular Dynamics simulation. Starting from the crystallographic coordinates, the protein shows a relaxation in water with an overall root mean square deviation from the crystal structure increasing up to 0.17 nm, within the first nanosecond. Then a plateau is reached and the molecule fluctuates around an equilibrium conformation. The results obtained in the first nanosecond are in agreement with those of a previous simulation (Diaz et al., J. Am. Chem. Soc., (2003) 125, 672–684). The successive equilibrium conformation in solution shows an increased mobility characterized by the following aspects. A flap-like translational motion anchores the Ω-loop to the body of the enzyme. A relevant part of the backbone dynamics implies a rotational motion of one domain relative to the other. The water molecules in the active site can exchange with different residence times. The H-bonding networks formed by the catalytic residues are frequently interrupted by water molecules that could favour proton transfer reactions. An additional simulation, where the aspartyl dyad D214–D233 was considered fully deprotonated, shows that the active site is destabilized.     

钒氧阴离子团簇与小分子碳氢化合物反应的实验和理论研究

为了在分子层次上揭示相关催化反应的机理, 人们对过渡金属氧化物团簇与碳氢化合物分子反应进行了大量研究. 相比于过渡金属氧化物团簇阳离子, 阴离子对一些碳氢化合物的活性弱得多, 因此研究还很少. 在本工作中, 我们通过激光溅射产生钒氧团簇阴离子VxOy, 产生的团簇在接近热碰撞条件下与烷烃(C2H6和C4H10)以及烯烃(C2H4和C3H6) 在一个快速流动反应管中进行反应, 飞行时间质谱用来检测反应前后的团簇分布. 在VxOy与烷烃的反应中, 生成了产物V2O6H-和V4O11H-; 在与烯烃的反应中, 产生了相应的吸附产物V4O11X-(X=C2H4或C3H6). 密度泛函理论计算表明: V2O-6和V4O-11可以活化烷烃(C2H6和C4H10)的C—H键, 也可以与烯烃(C2H4和C3H6)发生3+2环化加成反应形成一个五元环结构(-V-O-C-C-O-), C—H键活化与环加成反应都需经历可以克服的反应能垒. 理论计算与实验观测结果相符合. V2O-6和V4O-11团簇都具有氧原子自由基(O·或O-)的成键特征, 活性O-物种也经常出现在钒氧催化剂表面, 因而本研究在分子水平上, 揭示了表面活性氧物种与碳氢化合物反应的机理.     

Nonproteolytic cleavage of aspartyl proline bonds in the cellulosomal scaffoldin subunit from Clostridium thermocellum

Previous work from our group [Morag (Morgenstern), E., Bayer, E. A., and Lamed, R. (1991), Appl. Biochem. Biotechnol. 30, 129–136] has demonstrated an anomalous electrophoretic mobility pattern for scaffoldin, the 210-kDa cellulosome-integrating subunit of Clostridium thermocellum. Subsequent evidence [Morag, E., Bayer, E. A., and Lamed, R. (1992), Appl. Biochem. Biotechnol. 33, 205–217] indicated that the effect could be attributed to a nonproteolytic fragmentation of the subunit into a defined series of lowermolecular-weight bands. In the present work, a recombinant segment of the scaffoldin subunit was employed to determine the site(s) of bond breakage. An Asp-Pro sequence within the cohesin domain was identified to be the sensitive peptide bond. This sequence appears quite frequently in the large cellulosomal proteins, and the labile bond may be related to an as yet undescribed physiological role in the hydrolysis of cellulose by cellulosomes.     

Expression of Catalytic Domain of Protein Tyrosine Phosphatase 1B and Preparation of Its Polyclonal Antibody

This study focuses on the expression of human protein tyrosine phosphatase 1B(PTP1B) catalytic domain (△PTP1B) and preparation of polyclonal antibody against △PTP1B. △PTP1B gene was PCR amplified with the cDNA of human PTP1B as the template, and cloned into the pT7 expression vector. The recombinant pT7-△PTP1B was expressed in E. coli Rosetta( DE3 ) host cells and purified. The antiserum was prepared by immunizing rabbit with purified recombinant △PTP1B. The polyclonal antibody against △PTP1B was purified by PVDF immobilized antigen affinity chromatography. △PTP1B was correctly cloned, expressed, and purified as confirmed by PCR, DNA sequence ratio) and 0. 1 ng, respectively. This study provides an important basis for further studying the biological function of PTP1B and its relationship with human diseases.     

Discovery of Cell‐Permeable Inhibitors That Target the BRCT Domain of BRCA1 Protein by Using a Small‐Molecule Microarray

BRCTs are phosphoserine‐binding domains found in proteins involved in DNA repair, DNA damage response and cell cycle regulation. BRCA1 is a BRCT domain‐containing, tumor‐suppressing protein expressed in the cells of breast and other human tissues. Mutations in BRCA1 have been found in ca. 50 % of hereditary breast cancers. Cell‐permeable, small‐molecule BRCA1 inhibitors are promising anticancer agents, but are not available currently. Herein, with the assist of microarray‐based platforms, we have discovered the first cell‐permeable protein–protein interaction (PPI) inhibitors against BRCA1. By targeting the (BRCT)₂ domain, we showed compound 15 a and its prodrug 15 b inhibited BRCA1 activities in tumor cells, sensitized these cells to ionizing radiation‐induced apoptosis, and showed synergistic inhibitory effect when used in combination with Olaparib (a small‐molecule inhibitor of poly‐ADP‐ribose polymerase) and Etoposide (a small‐molecule inhibitor of topoisomerase II). Unlike previously reported peptide‐based PPI inhibitors of BRCA1, our compounds are small‐molecule‐like and could be directly administered to tumor cells, thus making them useful for future studies of BRCA1/PARP‐related pathways in DNA damage and repair response, and in cancer therapy.     

钒氧阴离子团簇与小分子碳氢化合物反应的实验和理论研究(英文)

为了在分子层次上揭示相关催化反应的机理,人们对过渡金属氧化物团簇与碳氢化合物分子反应进行了大量研究.相比于过渡金属氧化物团簇阳离子,阴离子对一些碳氢化合物的活性弱得多,因此研究还很少.在本工作中,我们通过激光溅射产生钒氧团簇阴离子VxOy-,产生的团簇在接近热碰撞条件下与烷烃(C2H6和C4H10)以及烯烃(C2H4和C3H6)在一个快速流动反应管中进行反应,飞行时间质谱用来检测反应前后的团簇分布.在VxOy-与烷烃的反应中,生成了产物V2O6H-和V4O11H-;在与烯烃的反应中,产生了相应的吸附产物V4O11X-(X=C2H4或C3H6).密度泛函理论计算表明:V2O6-和V4O1-1可以活化烷烃(C2H6和C4H10)的C-H键,也可以与烯烃(C2H4和C3H6)发生3+2环化加成反应形成一个五元环结构(-V-O-C-C-O-),C-H键活化与环加成反应都需经历可以克服的反应能垒.理论计算与实验观测结果相符合.V2O6-和V4O1-1团簇都具有氧原子自由基(O·或O-)的成键特征,活性O-物种也经常出现在钒氧催化剂表面,因而本研究在分子水平上,揭示了表面活性氧物种与碳氢化合物反应的机理.     

Confirmatory analysis of Trenbolone using accurate mass measurement with LC/TOF-MS

The use of accurate mass measurement as a confirmation tool is examined on a TOF-MS and compared with confirmation using a triple quadrupole mass spectrometer (QqQ-MS). Confirmation of the identity of a substance using mass-spectrometric detection has been described. However, the use of accurate mass measurement for confirmatory analysis has not been taken into account. In this study, criteria for confirmation with accurate mass are proposed and feasibility is demonstrated. Mass accuracy better than 3 ppm of the quasi-molecular ion and a fragment and their relative ratios determined with LC/TOF-MS are compared to the criteria of two transition ions and their ratio of LC/QqQ-MS. The results show that these criteria can be met for Trenbolone in samples of bovine urine and that single MS accurate mass measurement is comparable to nominal mass MS/MS for confirmation. The increase in popularity and availability of LC/TOF-MS instruments and the ease, of which exact masses can be measured, make it important to formulate criteria for this type of instrumentation. It is shown in this study that accurate mass measurement can be used for confirmatory analysis. However, more experiments need to be conducted to demonstrate the applicability of accurate mass measurement in general for residue analysis.