磁场对Schiff碱配合物模拟甲烷单加氧酶催化性能的影响

生命体中存在许多双金属酶 ,其结构和作用机制目前尚不清楚 ,为了模拟甲烷单加氧酶的催化作用 ,我们将催化活性较高的金属卟啉、稳定性较高的 Schiff碱及双核结构结合起来 ,设计合成了一系列“类卟啉型”Schiff碱双核配合物 ,并将这些双核配合物模拟酶催化亚碘酰苯 (Ph IO)单加氧化环己烷反应 ,发现其催化活性及抗氧化稳定性类似于四芳基金属卟啉 [1～ 3 ] ;还发现在模拟酶催化环己烷氧化反应中双核配合物中的两个金属离子间存在协同作用 [4 ] .外加磁场对一般热化学反应影响较小 [5～ 7] ,而在催化反应中的磁场效应更明显 [5,8] .为了较…     

Schiff碱铜配合物模拟过氧化物酶的研究

两种Schiff碱铜配合物首次作为过氧化物酶的模拟物用于催化过氧化氢氧化苯酚的反应；分析了配合物的特征光谱；研究了Schiff碱铜配合物的催化氧化机理，建立了催化氧化反应动力学数学模型；讨论了过氧化氢／催化剂摩尔比、体系温度、体系pH和胶束微环境对催化反应速率的影响．结果表明：这两种Schiff碱铜配合物在不同的反应条件下均表现出过氧化物酶催化的特征．     

Schiff碱配合物催化过氧化氢氧化苯酚的动力学研究

按照文献方法合成了钴(Ⅱ)和铁(Ⅱ)Schiff碱配合物，研究了它们作为模拟过氧化物酶在缓冲溶液中以及在三种不同的表面活性剂(CTAB，Brij35，LSS)胶束中催化过氧化氢氧化苯酚的反应，结果表明：过氧化氢／配合物物质的量比和胶束微环境对金属配合物催化过氧化氢氧化苯酚的反应有明显的影响；本文所提出的Schiff碱金属配合物催化苯酚氧化反应的机理和动力学数学模型是合理的。     

呋喃胺水杨醛Schiff碱铜(Ⅱ)配合物的合成与结构

以4,5-二甲基-3-腈基-2-呋喃胺与水杨醛为原料,合成了4,5-二甲基-3-腈基-2-呋喃胺水杨醛Schiff碱化合物,再与醋酸铜反应得到一种新型的呋喃胺水杨醛Schiff碱铜(Ⅱ)配合物.目标化合物通过IR、UV,元素分析及摩尔电导分析等进行了表征.应用荧光光谱法研究了该配合物与牛血清白蛋白(BSA)之间的相互作用.实验表明,该配合物能强烈猝灭BSA的内源荧光.     

一种树状桥联水杨醛亚胺配体的合成与表征

以甲醇为溶剂,将具有配位能力的水杨醛(2)通过Schiff碱缩合反应接枝到整代聚酰胺-胺(1)骨架上,合成了一种树状桥联水杨醛亚胺配体,其结构经1H NMR,IR和元素分析表征.最佳反应条件为:1 4 mmol,n(1):n(2)=1:6,甲醇30 mL,于65℃反应5 h,产率在90%以上.     

水杨醛缩牛磺酸Schiff碱和还原Schiff碱的合成、晶体结构及其荧光性质

在甲醇溶液中,水杨醛和牛磺酸经缩合反应合成了水杨醛缩牛磺酸Schiff碱(1);1用硼氢化钠还原制得对应的其还原Schiff碱(2).1和2的结构经1H NMR,IR和元素分析表征.X-射线单晶衍射分析表明,2属单斜晶系,空间群P21/c,晶胞参数a=10.787 4(12)A,b=8.989 7(10)A,c=11....     

Mn_3O(Salea)_2(C_2H_3O_2)_3·HC_2H_3O_2的合成、表征及放氧活性测定

合成了三核锰(Ⅲ)Schiff碱配合物:Mn_3O(Salea)_2(C_2H_3O_2)_3·HC_2H_3O_2(其中Salea~(2-)为水杨醛缩乙醇胺Schiff碱阴离子),经元素分析、磁矩、化合价、电导率、热分析、红外、紫外光谱等进行表征,并利用氧电极进行了放氧活性测试,发现在对苯醌存在下配合物能促使水分解释放氧气,其反应受温度、对苯醌和配合物浓度等因素影响,并提出了可能的放氧反应方程.     

Schiff碱配合物模拟酶催化性能的结构效应研究

研究了新型Schiff碱双锰及双铁配合物在模拟酶催化PhIO单加氧化环己烷反应及被PhIO氧化破坏反应中的结构效应.结果表明,随着这些配合物的环内空腔逐渐增大,其抗氧化稳定性、催化活性及催化反应产率依次降低.配合物中最佳螯合环为五元环.     

Schiff碱镧配合物的合成及其催化烷基异氰酸酯聚合

通过氯化镧与Schiff碱钠盐(NaSalen)的交换反应制备了4种镧的Schiff碱配合物La(HSalen1-4)3,对其中以3,5-二叔丁基水杨醛缩苯胺为配体的配合物La(HSalen2)3进行了X-射线单晶衍射分析,测定其单晶结构为五角双锥构型,七配位的镧金属中心与氮和氧原子相连.将所得的La(HSalen)3...     

新型含香豆素骨架水杨醛类Schiff碱衍生物的合成

在无溶剂条件下,以草酸为催化剂,间苯二酚与乙酰乙酸乙酯经Pechmann反应制得7-羟基-4-甲基香豆素(1);1经硝化、还原制得3-氨基7-羟基4-甲基香豆素(2);2与取代水杨醛经缩合反应合成了四个新的含香豆素骨架水杨醛类Schiff碱衍生物,其结构经1H NMR,IR和元素分析表征.     

Antioxidant Effect of Human Selenium-containing Single-chain Fv in Rat Cardiac Myocytes

Reactive oxygen species(ROS) plays a key role in human heart diseases.Glutathione peroxidase(GPX) functions as an antioxidant as it catalyzes the reduction of hydroperoxide.In order to investigate the antioxidant effect of human selenium-containing single-chain Fv(Se-scFv-B3),a new mimic of GPX,a model system of hydrogen peroxide(H2O2)-induced rat cardiac myocyte damage was established.The cardiac myocyte damage was characterized in terms of cell viability,lipid peroxidation,cell membrane integrity,and intracellular H2O2 level.The Se-scFv-B3 significantly reduced H2O2-induced cell damage as shown by the increase of cell viability,the decline of malondialdehyde(MDA) production,lactate dehydrogenase(LDH) release,and intracellular H2O2 level.So Se-scFvB3 may have a great potential in the treatment of human heart diseases induced by ROS.     

Antioxidant Effect of Selenium-containing Glutathione S-Transferase in Rat Cardiomyocytes

As one of the most important antioxidant enzymes, glutathione peroxidase(GPX) protects cells and tissues from oxidative damage, and plays an important role in cardiovascular and cerebrovascular injuries induced by oxidative stress. The antioxidant effect of selenium-containing glutathione S-transferase(Se-GST), a mimic of GPX was investigated on rat cardiomyocytes. To explore the protection function of Se-GST in hydrogen peroxide(H₂O₂) challenged rat cardiomyocytes, we examined malondialdehyde(MDA), lactate dehydrogenase(LDH), superoxide dismutase( SOD) and cell apoptosis. The results demonstrate exposure of rat cardiomyocytes to H₂O₂ for 6 and 12 h induced the significant increases of MDA, LDH and apoptosis rate of cardiomyocytes, but pretreatment of rat cardiomyocytes with Se-GST at 0.0005 or 0.001 unit/mL prevents oxidative stress induced by H₂O₂ with the decreases of cell apoptosis. All the results hint Se-GST has antioxidant activity for oxidative stress challenged rat cardiomyocytes.     

以透明质酸为骨架的新型谷胱甘肽过氧化物酶(GPX)模拟酶的制备及性质研究

用修饰法合成以透明质酸为骨架的两种新型GPX模拟酶: 硒化透明质酸SeHA及碲化透明质酸TeHA. 用红外光谱和核磁共振波谱对模拟酶的结构进行研究, 证明其修饰位点位于透明质酸的N-乙酰氨基葡萄糖的—CH2OH. 用二硫代双硝基苯甲酸(DTNB)法测定模拟酶的硒含量为1.2%. 通过模拟酶对3种不同底物过氧化氢(H2O2)、过氧化氢正丁烷(t-BuOOH)和过氧化氢异丙苯(CuOOH)的催化活性的研究结果表明CuOOH为该反应的最佳底物. 研究模拟酶催化谷胱甘肽(GSH)还原3种过氧化物的动力学发现, 反应速率与底物浓度的双倒数曲线均为平行的直线, 说明模拟酶反应的动力学机制与天然GPX相同, 为乒乓机制. 用2,4-二叔丁基甲基苯酚(BHT)法证明了该催化反应为非自由基机理, 且模拟酶不易被碘乙酸抑制.     

Self‐Assembly of Multi‐nanozymes to Mimic an Intracellular Antioxidant Defense System

In this work, for the first time, we constructed a novel multi‐nanozymes cooperative platform to mimic intracellular antioxidant enzyme‐based defense system. V₂O₅ nanowire served as a glutathione peroxidase (GPx) mimic while MnO₂ nanoparticle was used to mimic superoxide dismutase (SOD) and catalase (CAT). Dopamine was used as a linker to achieve the assembling of the nanomaterials. The obtained V₂O₅@pDA@MnO₂ nanocomposite could serve as one multi‐nanozyme model to mimic intracellular antioxidant enzyme‐based defense procedure in which, for example SOD, CAT, and GPx co‐participate. In addition, through assembling with dopamine, the hybrid nanocomposites provided synergistic antioxidative effect. Importantly, both in vitro and in vivo experiments demonstrated that our biocompatible system exhibited excellent intracellular reactive oxygen species (ROS) removal ability to protect cell components against oxidative stress, showing its potential application in inflammation therapy.     

A semisynthetic glutathione peroxidase with high catalytic efficiency. Selenoglutathione transferase

Glutathione peroxidase (GPX) protects cells against oxidative damage by catalyzing the reduction of hydroperoxides by glutathione (GSH). GPX therefore has potential therapeutic value as an antioxidant, but its pharmacological development has been limited because GPX uses a selenocysteine as its catalytic group and it is difficult to generate selenium-containing proteins with traditional recombinant DNA technology. Here, we show that naturally occurring proteins can be modified to generate GPX activity. The rat theta-class glutathione transferase T2-2 (rGST T2-2) presents an ideal scaffold for the design of a novel GPX catalyst because it already binds GSH and contains a serine close to the substrate binding site, which can be chemically modified to bind selenium. The modified Se-rGST T2-2 efficiently catalyzes the reduction of hydrogen peroxide, and the GPX activity surpasses the activities of some natural GPXs.     

GSH对两种谷胱甘肽过氧化物酶模拟物活性影响的研究

设计并合成了谷胱甘肽过氧化物酶(GPX)模拟物6A,6A’-二苯胺-6B,6B’-二硒桥联-β-环糊精(6-AnSeCD). 采用双酶偶联法测定GPX的活力结果显示, 6A,6A’-二环己胺-6B,6B’-二硒桥联-β-环糊精(6-CySeCD)催化谷胱甘肽还原H2O2和枯烯H2O2的活力均比6-AnSeCD的高. 为了进一步考察6-CySeCD和6-AnSeCD与GSH之间的相互作用, 进行了分子动力学(MD)模拟和分子对接研究. 结果表明, 与GSH的结合使GPX模拟物的构象发生变化, 这种改变可能是影响桥连GPX模拟物催化活性的关键因素.     

Preparation and Kinetics of a Novel Glutathione Peroxidase Mimic- Selenium-modified Hyaluronic Acid

A selenium-modified hyaluronic acid（HA） compound（SeHA） was synthesized as a mimic of glutathione peroxidase（GPX）. IR and NMR spectra of SeHA predict that the --CH2OH group of the N-acetyl-D-glucosamine in HA was modified by group --Sell. There are averagely 152 --Sell groups in one SeHA molecule. The GPX activities are 103.88, 32. 15 and 152. 71 U/μmol, respectively, when the substrates were H2O2, BuOOH and CuOOH. Ping-pong mechanism was observed in the steady-state kinetic studies of the reactive oxygen species（ROS） consuming reaction. Result of reactions of SeHA with free radical capturer 2,6-di-tert-butyl-4-methylphenol（BHT） shows that the catalysis is based on a non-free radical-mechanism and the SeHA can not be inhibited by iodoacetate, an enzyme inhibitor.     

Protection of mitochondrial integrity from oxidative stress by selenium-containing glutathione transferase

The antioxidant activity of a novel artificial glutathione peroxidase-like enzyme, selenium-containing glutathione 5-transferase from Lucilia cuprina (seleno-LuGST1-1), was studied by using a ferrous sulfate/ascorbate-induced mitochondrial damage model system. Swelling of mitochondria, lipid peroxidation, and cytochrome-c oxidase activity were selected to evaluate the preservation of mitochondrial integrity in this system. Seleno-LuGST1-1 could effectively protect the mitochondria against oxidative damage in a dose-dependent manner and exhibited both higher catalytic activity and greater antioxidant ability than the classic mimic, 2-phenyl-1,2-benziososelenazol-3(2H)-one (Ebselen). This novel artificial biocatalyst therefore may have great protential for pharmacologic application in the treatment of reactive oxygen species-related diseases.     

Comparison of the effects of different antiviral treatments on the antioxidant systems of stroma-free hemoglobin

The effect of virus inactivation by 1,9-dimethylmethylene blue (DMMB) phototreatment, methylene blue (MB) phototreatment or heat on the activities of antioxidant systems of stroma-free hemoglobin (SFH) was studied. DMMB photoinactivated human immunodeficiency virus by > 3.69 log10 under conditions that inactivated 3.33 log10 of vesicular stomatitis virus (VSV). Under conditions which inactivated VSV by 6.10 log10 (1.37 J/cm2 irradiation and 2 microM DMMB), there was little change in the methemoglobin (Met-Hb) formation, concentration of reduced glutathione (GSH), or superoxide dismutase (SOD), catalase (CAT) or glutathione peroxidase (GPX) activities. However, the activity of glutathione reductase (GR) was decreased by 77%. Under conditions that inactivated VSV by 5.69 log10 (1.37 J/cm2 irradiation and 24 microM MB) there was little effect of MB phototreatment on SOD, CAT, GPX and GSH activities. However, GR activity was decreased by 74% and Met-Hb content reached 3.98%. Under conditions that inactivated VSV by more than 6.20 log10 (60 degrees C for 2 min), virucidal heat treatment resulted in 27% Met-Hb formation and decreased GPX activity by 43%. No significant decline in SOD, CAT or GR activities or GSH concentration was observed. These results suggest that, compared with heat treatment and MB phototreatment, virucidal DMMB treatment preserves not only the oxidative state of hemoglobin but also the antioxidant systems against superoxide and hydrogen peroxide, although the reduced GR activity may limit the quenching capacity of antioxidants in DMMB-treated SFH.     

Selection of phage antibodies with GPX activity by combination of phage displayed antibody library with chemical modification and their characterization using a surface plasmon resonance biosensor

Glutathione peroxidase (GPX) is an important antioxidant enzyme, which plays an important role in scavenging reactive oxygen species. To obtain humanized GPX catalytic antibodies, the phage displayed human antibody library on the surface of the filamentous bacteriophage was used to select novel antibodies by repetitive screening. Phage antibodies B8, H6 and C1 with the GSH-binding site were obtained from the library by enzyme-linked immunosorbent assay (ELISA) analysis with four rounds of selection against three haptens, S-2,4-dinitrophenyl t-butyl ester [GSH-S-DNP-Bu (B)], S-2,4-dinitrophenyl t-hexyl ester [GSH-S-DNP-He (H)] and S-2,4-dinitrophenyl cycle-hexyl ester [GSH-S-DNP-cHe (C)], and characterized using surface plasmon resonance (SPR) biosensor. The gold layer was modified by dithiodiglycolic acid (DDA) and three haptens were easily attached to DDA by self-assembling to form a biosensor membrane. The membrane bounds specifically corresponding antibodies. The kinetic process of the reaction between phage antibodies and their haptens was studied by SPR biosensor. In order to improve selectivity, chemical modification was used to incorporate directly catalytic group selenocysteine (Sec) into selected phage clone B8, H6 and C1 to form Se-B8, Se-H6 and Se-C1, respectively. The GPX activities of Se-B8, Se-H6 and Se-C1 were found to be 3000, 2000 and 700 units/μmol, respectively. Compared with conventional ELISA analysis, the proposed method based on SPR biosensor is much more rapid and simpler.