8-羟基喹啉单体及二聚体质子转移反应的理论研究

Density functional theory （DFT） of quantum chemistry method was employed to investigate proton transfer reactions of 8-hydroxyquinoline （8-HQ） monomers and dimers. By studying the potential energy curves of the isomerization, the most possible reaction pathway was found. The total energy of 8-hydroxyquinoline was lower than that of quinolin-8（1H）-one, whereas the order was reversed in dimers. The findings explained the contrary experimental phenomena. The minimum reaction barrier of intramolecular proton transfer was 47.3 kJ/mol while that in dimer was only 25.7 kJ/mol. Hence it is obvious that proton transfer reactions of 8-HQ monomer have a considerable rate but it is easier to proceed for 8-HQ dimer than monomers. It implied that the hydrogen bond played an important role in depressing the activation energy of reaction. The mechanism of the tautomerization was discussed on the basis of theoretical results.     

Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2

Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window （180-190 ℃） for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas.     

ACTIVE INTERMEDIATES IN PHOTORADICAL AGING OF POLYMERS

The data referring to the mechanism and efficiency of electronically excited macroradical and radical anionreactions, the important role of photochemical chain reactions in polymers are presented, It was found that by varying photonenergy, temperature, photolysis time and competition between thermal and photochemical reactions, it is possible to change the functional composition and molecular weight distribution of polymers.     

A Concise Approach to the Synthesis of Carnosic Acid Type Diterpenes

AIDS has seriously affected human being's health and about 13.9 million people have been killed by AIDS in the world. So far, A. Paris et al1 found that Carnosic acid and its analogs posses inhibitory effect on HIV-1 protease and HIV virus replication activity. In order to clarify the structure-active relationship of this kind of compounds, a concise approach was designed, which is a convergent synthesis. Best to our knowledge, it is the first successful convergent route in total synthes…     

Effect of Different Energy Sources on Ochrobactrum anthropi Bacteria Chromium Reduction

Ochrobactrum anthropi CTS-325 isolated from a chromium-contaminated site had better resistance to Cr(Ⅵ) in LB medium under aerobic condition.Meanwhile,it was found that the reduction of Cr(Ⅵ) is not complete during the experimental process.Therefore,a series of small molecule energy sources including nitrogen and carbon sources were added into the LB medium in the bacterial stationary phase to promote the chromium reducibility.The result showed that the bacterial growth was positively correlated with the chromium reduction.SDS-PAGE analysis indicated that the protein groups were changed when the bacteria were stimulated by the chromium.Additionally,it was revealed that O.anthropi CTS-325 could utilize the cheaper alternative of sugar(sucrose residue leaching solution) well for further growth and restart the chromium reduction,which offered a new method for practical appli-cations.     

Preparation of the Ag2O2-PbO2 Modified Electrode and Its Application towards Escherichia coli Fast Counting in Water

A novel nano crystalline Ag2O2-PbO2 film chemically modified electrode (CME) was prepared and the CME was characterized by X-ray diffractometer (XRD) and atomic focrce microscope (AFM). By chronoamperometry, the nano Ag2O2-PbO2 CME was used as bioelectrochemical sensor to determine the population of Escherichia coli (E.coli) in water. Compared with conventional methods, it is found that the technique we used is fast and convenient in counting E.coil     

环烯丙基溴在Cu/SnCl2参与的水相羰基烯丙基化反应中的应用

Five- and six-membered cyclic allylic halides were found to be much less reactive than the acyclic allylic halides in aqueous allylation reactions. Nevertheless, it was found that SnC12/Cu was powerful enough to mediate the aqueous allylation reactions involving cyclic allylic halides. Both the aliphatic and aromatic aldehydes could be efficiently allylated and the reaction condition was mild, simple and safe. The yields were usually in 75%-97% and the reaction was erythro selective.     

Thioxanthene-9-thione Mediated MMA Polymerization

In the "cycloketyl radical mediated living polymerization"(CMP) process, a cycloketyl compound, [9,9′]bixanthenyl-9,9′ diol(BIXAN) was ultilized as initiator and mediator. The cycloketyl(CK) radical was used as the dormant radical to achieve the increase of molecular weight. Herein, a series of cycloketyl thioketones were synthesised by Lawesson's reagent by one step reaction with high yeild,and we found that, when a special cycloketyl thioketone compound, thioxanthene-9-thione(TXT), was added to a routine radical polymerization system, TXT could capture chain radical, and simultaneously formed an radical analogous to CK radical in structure,which could trigger the growth of polymer chains. This simple system was efficient to initiate the polymerization of methyl methacrylate(MMA) and in all cases the molecular weights increased with the increase of conversions. By the end-group analysis with 1 H-NMR and MALDI-TOF MS, it was confirmed that the P-STXT radical was used to control the polymerization. The re-initiating reactions were achieved when PMMA was used as the macro-initiator.     

Microcalorimetric Study of the Biological Effects of Zn^＋ on Bacillus thuringiensis Growth

A microcalorimetric technique was used to investigate the influence of Zn^2 on the growth metabolism of Bacillus thuringiensis .LKB-2277 Bioactivity Monitor was employed to obtain the power-time curves,from which the maximum peak-heat output power(Pmax) in the log phase,the growth rate constants(k), the inhibitory ratios(I) ,the generational time(tG) and the total heat effect (Qtotal) in 23 h for the growth metabolism of Bacillus thuringiensis at 28℃ can be evaluated,The results indicate that the concentration of Zn^2 affects its growth obviously,Low concentration (0-50μg/mL) of Zn^2 promotes the growth of Bacillus thuringiensis while high concentration (50-500μg/mL) of Zn^2 inhibits its growth .When the concentration reached up to 600μg/mL,it can not grow at all.     

INHIBITORY PROPERTY CHARACTERIZATION AND REACTIVE SITE EXPLORATION OF THE ARROWHEAD PROTEINASE INHIBITOR

Affinity chromatography was used to separate two components A and B of the crystalline arrowhead proteinase inhibitor. Both A and B are double-headed and multifunctional proteinase inhibitors. Inhibitor A is capable of inhibiting equimolarly trypsin and chymo-trypsin simultaneously, and has a weak inhibitory activity toward kallikrein; whereas inhibitor B can inhibit two molecules of trypsin simultaneously, and shows rather higher inhibitory activity toward kallikrein than inhibitor A, but its inhibitory activity toward chymo-trypsin is much weaker than that of inhibitor A. The results of chemical modification and the competitive binding of trypsin and chymotrypsin with inhibitor A showed that the two reactive sites of both inhibitors A and B are Lys and Arg residues. Among them the Lys reactive site is specific for inhibiting mainly trypsin, whereas the active domain composed of the Arg reactive site appears to be multifunctional and capable of inhibiting many different Ser proteinases. Based on the st     

一个具有相反光学选择性的新颖海洋 GDSL脂肪酶MT6用于（S）-1-苯基乙醇制备

1-苯乙醇是一种重要的手性药物中间体,并且(S)-1-苯乙醇和(R)-1-苯乙醇均具有应用价值.怎样获得光学醇的1-苯乙醇是药物合成中的重要问题.传统的化学合成手段不仅反应过程复杂,而且反应条件剧烈,对环境污染严重,因此生物催化方法越来越受到重视.脂肪酶和酯酶以其出色的立体选择性和温和的反应条件而被广泛用于手性药物的拆分制备.但是之前的一些研究发现脂肪酶和酯酶大都对(R)-1-苯乙醇及其衍生物有选择性,而我们发现并鉴定的脂肪酶 MT6的立体选择性则与这些脂肪酶/酯酶完全相反,具体体现在以下两个方面：(1) MT6能够特异地催化(S)-1-苯乙醇和乙酸异丙烯酯的转酯反应,生成(R)-1-苯乙醇;(2) MT6能够选择性地水解(S)-乙酸苏合香酯,生成(S)-1-苯乙醇.可见,利用 MT6催化的转酯反应和水解反应可以巧妙地进行(S)-1-苯乙醇和(R)-1-苯乙醇的制备. MT6来源于深海放线菌Marinactinospora thermotolerans SCSIO 00652,属于 GDSL家族脂肪酶第 II类群,这一类群的脂肪酶绝大多数来自微生物.有关 GDSL家族脂肪酶在手性拆分中的应用研究非常少.我们之前报道了 MT6的克隆、表达、纯化及转酯拆分反应,本文重点考察了 MT6通过水解反应制备(S)-1-苯乙醇的条件,优化了酶促水解拆分反应温度、有机共溶剂、pH、离子强度、酶用量、底物浓度、反应时间以及底物侧链长度等参数.研究发现,在反应体系中加入一定量的有机共溶剂能够大大提高产物(S)-1-苯乙醇的光学纯度,其中添加二氯甲烷获得的结果最为理想,可以将产物光学纯度从43%提高到89%,E值从2.84提高至22.82.经过优化,最佳反应温度为40°C,共溶剂二氯甲烷浓度为5%(体积分数),反应缓冲液为0.1 mol/L Tris-HCl (pH =7.0),酶用量为150 mg/mL,底物为15 mmol/L乙酸苏合香酯,反应时间控制在12 h.在此条件下,制备的(S)-1-苯乙醇的光学纯度可达97%,转化率可达28.5%,E值为95.9.此外,还比较了侧链长度不同的1-苯基乙醇酯对水解反应的影响,结果表明1-苯基乙醇酯的侧链长度可极大影响光学选择性和产率.在反应条件相同时, MT6催化侧链长度为4个碳的丁酸-1-苯乙酯水解,生成(S)-1-苯乙醇的光学纯度仅为50%.利用 AutoDock软件进行分子对接,结果显示长侧链的1-苯基乙醇酯离活性中心 His230的咪唑基较远,可能是导致酶立体选择性低的重要原因.值得注意的是,海洋微生物来源的 GDSL脂肪酶 MT6在水解反应和转酯反应中均表现出与一些已知脂肪酶/酯酶相反的立体选择性,因而具备进一步开发和应用价值.所制备的(S)-1-苯乙醇的光学纯度为97%,可以通过和转酯反应相结合的方式进一步提高产物的光学纯度和转化率.     

金属硫蛋白与Cd2+、Pb2+络合反应的微量量热滴定

Metallothionein, a class of low molecular weight, metal- and cysteine-rich Proteins, are postulated to play a central role in metal-related biological processes such as the detoxification of Cd2+and Pb2+. The thermal Properties of the interactions of rabbit liver Zn_7MT2 and apo-MT2 with Cd2+ and Pb2+ were studied using isothermal titration calorimeter. The same product Cd_7MT formed in the reactions of Cd2+ with Zn_7MT2 and apo-MT2, while the reactions of Ph2+ with Zn_7MT2 and apo-MT2 Produced two MT species Ph_7MT and Ph_7MT'. The thermodynamic parameters (△H、 △G、 △S, etc. ) for the reactions of MT with 1 mol metal ions were measured at 293.15 K, pH 4.70. All of these reactions are spontaneous, exothermic processes. The values of △G and K show that Cd2+ is more affinitive to MT than Ph2+. The equilibrium constants K of the replacement reactions of Zn_7MT2 by 1 mol Cd2+ and Pb2+ are 2. 7×105 and 1. 3×105 respectively, that means the concentrations of free Cd2+ and Pb2+ are depressed to about 1. 0×10-5 after the reactions with Zn_7MT2. These data can be used to evaluate quantitatively the ability of MT in Cd2+ and Pb2+ detoxificatio.     

Genotyping of the human lipoprotein lipase gene by ferrocenylnaphthalene diimide-based electrochemical hybridization assay.

A ferrocenylnaphthalene diimide (FND)-based electrochemical hybridization assay (FND-EHA) was applied to the detection of two mutations in human lipoprotein lipase (LPL) gene, G188E (one base transition) and Arita (one base deletion). A probe oligodeoxyribonucleotide of 13 bases representing the wild type (WT) sequence of LPL was immobilized on a gold electrode, followed by hybridization with a sample PCR product of 350 base pairs under conditions in which both WT and mutated (MT) sequences could form a duplex with the probe. The hybridized electrodes were soaked in an electrolyte containing FND under conditions in which only the mismatched duplex could undergo dissociation. FND was concentrated in proportion to the amount of the duplex remaining on the electrode to give rise to a current signal. Blind tests were run to judge the genotype (WT/WT, WT/MT, or MT/MT) of 10 samples each for the G188E and Arita mutations and then, 8 and 10 of them were judged correctly, respectively.     

Arsenic binding to human metallothionein

The number of reported cases of chronic arsenic poisoning is on the rise throughout the world, making the study of the long-term effects of arsenic critical. As(3+) binds readily to biological thiols, including mammalian metallothionein (MT), which is an ubiquitous sulfur-rich metalloprotein known to coordinate a wide range of metals. The two-domain mammalian protein binds divalent metals (M) into two metal-thiolate clusters with stoichiometries of M(3)S(cys9) (beta) and M(4)S(cys11) (alpha). We report that As(3+) binds with stoichiometries of As(3)S(cys9) (beta) and As(3)S(cys11) (alpha) to the recombinant human metallothionein (rhMT) isoform 1a protein. Further, we report the complete kinetic analysis of the saturation reactions of the separate alpha and beta domains of rhMT with As(3+). Speciation in the metalation reactions was determined using time- and temperature-resolved electrospray ionization mass spectrometry. The binding reaction of As(3+) to the alpha and beta MT domains is shown to be noncooperative and involves three sequential, bimolecular metalation steps. The analyses allow for the first time the complete simulation of the experimental data for the stepwise metalation reaction of MT showing the relative concentrations of the metal-free, apo MT and each of the As-MT intermediate species as a function of time and temperature. At room temperature (298 K) and pH 3.5, the individual rate constants for the first, second, and third As(3+) binding to apo-alphaMT are 5.5, 6.3, and 3.9 M(-)(1) s(-)(1) and for apo-betaMT the constants are 3.6, 2.0, and 0.6 M(-)(1) s(-)(1). The activation energy for formation of As(1)-H(6)-betaMT is 32 kJ mol(-)(1), for As(2)-H(3)-betaMT it is 35 kJ mol(-)(1), for As(3)-betaMT it is 29 kJ mol(-)(1), for As(1)-H(8)-alphaMT it is 33 kJ mol(-)(1), for As(2)-H(5)-alphaMT it is 29 kJ mol(-)(1), and for As(3)-H(2)-alphaMT it is 23 kJ mol(-)(1).     

Atom‐Specific Mutagenesis Reveals Structural and Catalytic Roles for an Active‐Site Adenosine and Hydrated Mg2+ in Pistol Ribozymes

The pistol RNA motif represents a new class of self‐cleaving ribozymes of yet unknown biological function. Our recent crystal structure of a pre‐catalytic state of this RNA shows guanosine G40 and adenosine A32 close to the G53–U54 cleavage site. While the N1 of G40 is within 3.4 Å of the modeled G53 2′‐OH group that attacks the scissile phosphate, thus suggesting a direct role in general acid–base catalysis, the function of A32 is less clear. We present evidence from atom‐specific mutagenesis that neither the N1 nor N3 base positions of A32 are involved in catalysis. By contrast, the ribose 2′‐OH of A32 seems crucial for the proper positioning of G40 through a H‐bond network that involves G42 as a bridging unit between A32 and G40. We also found that disruption of the inner‐sphere coordination of the active‐site Mg²⁺ cation to N7 of G33 makes the ribozyme drastically slower. A mechanistic proposal is suggested, with A32 playing a structural role and hydrated Mg²⁺ playing a catalytic role in cleavage.     

A Study of Heterogeneous Catalysis by Nanoparticle‐Embedded Paper‐Spray Ionization Mass Spectrometry

We have developed nanoparticle‐embedded paper‐spray mass spectrometry for studying three types of heterogeneously catalyzed reactions: 1) Palladium‐nanoparticle‐catalyzed Suzuki cross‐coupling reactions, 2) palladium‐ or silver‐nanoparticle‐catalyzed 4‐nitrophenol reduction, and 3) gold‐nanoparticle‐catalyzed glucose oxidation. These reactions were almost instantaneous on the nanocatalyst‐embedded paper, which subsequently transferred the transient intermediates and products to a mass spectrometer for their detection. This in situ method of capturing transient intermediates and products from heterogeneous catalysis is highly promising for investigating the mechanism of catalysis and rapidly screening catalytic activity under ambient conditions.     

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

The angular and velocity distributions of desorbing product N(2) were examined over the crystal azimuth in steady-state NO+CO and N(2)O+CO reactions on Pd(110) by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N(2) desorption in both reactions splits into two directional lobes collimated along 41 degrees -45 degrees from the surface normal toward the [001] and [001] directions. Above 600 K, the normally directed N(2) desorption is enhanced in the NO reduction. Each product desorption component, as well as CO(2), shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.     

Synthesis,Characterization and Catalysis of Ce‐MCM‐41

The cerium‐containing MCM‐41 (Ce‐MCM‐41) has been synthesized by direct hydrothermal method. The low‐angle XRD patterns revealed the typical five major peaks of MCM‐41 type hexagonal structures. The interplanar spacing d₁₀₀ = 38.4 Å was obtained that can be indexed on a hexagonal unit cell parameter with a_o = 44.3 Å which was larger than that of pure siliceous MCM‐41 (Si‐MCM‐41). Transmission electron micrograph shows the regular hexagonal array of uniform channel characteristics of MCM‐41. The BET surface area of Ce‐MCM‐41 was 840 m²/g, which is much reduced as compared to that of Si‐MCM‐41, with the pore size of 26.9 Å and mesopore volume of 0.78 cm³/g were measured by nitrogen adsorption‐desorption isotherm at 77 K. Along with the results, the synthesized Ce‐MCM‐41 exhibited a well‐ordered MCM‐41‐type mesoporous structure with the incorporation of cerium. Using Ce‐MCM‐41 as a support, the Rh (0.5 wt%) catalyst exhibited very high activity for the NO/CO reactions.     

Investigation of mercury metallothionein complexes in tissues of rat after oral intake of HgCl2

Mercury, a highly toxic metal found widely throughout the environment, is a potent inducer of metallothionein (MT) expression. The role of MTs in the detoxification of mercury after its oral intake in mammals is studied. After feeding rats with mercuric chloride by gastric gavage, the distribution of heavy metals in rat tissues was investigated by inductively coupled plasma mass spectrometry (ICP‐MS). Extensive accumulation of mercury, copper and zinc in kidney and liver is observed. A homemade preparative size‐exclusion chromatography (SEC) column (30 cm × 1.9 cm) packed with Sephadex G‐75 (40–120 µm particle size) gel (Pharmacia) was used for the purification of MT fractions in rat tissues. Preliminary results from SEC indicate that the mercury‐binding MT levels in liver were much lower than in kidney. The MT fractions were collected, desalted, and then separated by reversed‐phase high‐performance liquid chromatography (HPLC) with UV–Vis spectrometry, ICP‐MS and electrospray ionization MS detection. One major and several minor peaks were observed in the HPLC chromatograms of the MT fraction for the kidney sample. UV absorption spectra indicate that MTs were found to bind with mercury. There were no significant mercury‐binding MTs detected in the liver sample using UV detection. ICP‐MS detection showed that mercury‐binding MTs in kidney contained large amounts of mercury and copper but little zinc. Further characterization with ESI‐MS showed that the major peak found in kidney contained Hg₆Cu, Hg₅Cu₂‐MT‐2c and Hg₆‐MT‐2β, Hg₆Cu‐MT‐1γ, Hg₇‐MT‐2α. However, distinction between copper and zinc could not be made based on current mass spectrometric analysis because of instrumental resolution limitations. Copyright © 2005 John Wiley & Sons, Ltd.     

Markovnikov versus anti‐Markovnikov addition and C–H activation: Pd–Cu synergistic catalysis

Copper‐ and palladium‐mediated transmetalation and coupling reactions are the backbone to several synthetic methodologies in organic chemistry for C–C bond formation. Computer‐aided simulations using density functional theory (DFT) (B3LYP‐D3 functional with 6‐31G** and effective core potential (ECP)‐LACVP** for heavy atoms for optimizations and cc‐pVTZ(?f) and ECP‐LACV3P** for single‐point calculations) was used to shed light on the probable mechanism of a novel synergistic Cu/Pd catalysts for the coupling of alkene, (Bpin)2 (where, pin = pinacolate), and vinyl‐ or aryl‐halogenated analogues. Every single conceivable pathway was carefully contemplated, and the base minimum energy pathway was found effectively. The copper‐catalyzed nucleophilic generation yields anti‐Markovnikov product using styrene as an alkene. This study affirms quantitatively and accurately how the reaction proceeds and at which steps of the synergistic catalysis the demand of the transmetalation and nucleophile formation for the C–C coupling using phosphine ligands arise. We conclude that the E and Z selectivity depends on the stereochemistry of the substrates used.