The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre

Hydrogenases are abundant enzymes that catalyse the reversible interconversion of H(2) into protons and electrons at high rates. Those hydrogenases maintaining their activity in the presence of O(2) are considered to be central to H(2)-based technologies, such as enzymatic fuel cells and for light-driven H(2) production. Despite comprehensive genetic, biochemical, electrochemical and spectroscopic investigations, the molecular background allowing a structural interpretation of how the catalytic centre is protected from irreversible inactivation by O(2) has remained unclear. Here we present the crystal structure of an O(2)-tolerant [NiFe]-hydrogenase from the aerobic H(2) oxidizer Ralstonia eutropha H16 at 1.5?? resolution. The heterodimeric enzyme consists of a large subunit harbouring the catalytic centre in the H(2)-reduced state and a small subunit containing an electron relay consisting of three different iron-sulphur clusters. The cluster proximal to the active site displays an unprecedented [4Fe-3S] structure and is coordinated by six cysteines. According to the current model, this cofactor operates as an electronic switch depending on the nature of the gas molecule approaching the active site. It serves as an electron acceptor in the course of H(2) oxidation and as an electron-delivering device upon O(2) attack at the active site. This dual function is supported by the capability of the novel iron-sulphur cluster to adopt three redox states at physiological redox potentials. The second structural feature is a network of extended water cavities that may act as a channel facilitating the removal of water produced at the [NiFe] active site. These discoveries will have an impact on the design of biological and chemical H(2)-converting catalysts that are capable of cycling H(2) in air.     

[（n-Bu）4N]2[X2Mo4O10（OCH3）2]的合成与表征

本文选用醌类配体菲醌和酚类配体1，2-二羟基萘，合成了具有相似结构、通式为[(n-Bu)4N]2[X2Mo4O10(OCH3)2](X=OC10H6O和OC14H8O)的二种四聚钼多酸配合物，进行了元素分析、核磁共振、红外光谱和热重分析等表征．并对菲醌与钼多酸配合时由醌式状态向酚式结构的还原进行了研究和探讨．     

六元瓜环与[Zn(H2O)6]2+的超分子自组装结构

利用X-射线衍射方法测定六元瓜环(Q[6])与[Zn(H2O)6]2 形成的超分子自组装结构。在该化合物结构中,每一个六元瓜环分子包结了一个1,4二氧六烷分子,与瓜环两端的锌水合离子形成一个分子胶囊结构,并通过锌离子上的配位水分子分别与相邻两瓜环端口的羰基氧原子通过氢键相互作用形成一维超分子链。     

从[MoS4]^2-制备一个[MoOS3]^2-型簇合物的低热固相反应机理

首次以含[MoS4]^2-离子的（NH4）2MoS4为原料,与Cu（AC）2.H2O和PPh3在空气中研磨使其发生固相反应得到红色的固体.将此固体经CH3CN萃取,放置几天后可得到红黑色单晶[MoCu3OS3（PPh3）3（CH3COO）].测试了其晶体结构,并对该低热固相反应的机理进行了研究.     

Structural snapshots along the reaction pathway of ferredoxin-thioredoxin reductase

Oxygen-evolving photosynthetic organisms regulate carbon metabolism through a light-dependent redox signalling pathway. Electrons are shuttled from photosystem I by means of ferredoxin (Fdx) to ferredoxin-thioredoxin reductase (FTR), which catalyses the two-electron-reduction of chloroplast thioredoxins (Trxs). These modify target enzyme activities by reduction, regulating carbon flow. FTR is unique in its use of a [4Fe-4S] cluster and a proximal disulphide bridge in the conversion of a light signal into a thiol signal. We determined the structures of FTR in both its one- and its two-electron-reduced intermediate states and of four complexes in the pathway, including the ternary Fdx-FTR-Trx complex. Here we show that, in the first complex (Fdx-FTR) of the pathway, the Fdx [2Fe-2S] cluster is positioned suitably for electron transfer to the FTR [4Fe-4S] centre. After the transfer of one electron, an intermediate is formed in which one sulphur atom of the FTR active site is free to attack a disulphide bridge in Trx and the other sulphur atom forms a fifth ligand for an iron atom in the FTR [4Fe-4S] centre--a unique structure in biology. Fdx then delivers a second electron that cleaves the FTR-Trx heterodisulphide bond, which occurs in the Fdx-FTR-Trx complex. In this structure, the redox centres of the three proteins are aligned to maximize the efficiency of electron transfer from the Fdx [2Fe-2S] cluster to the active-site disulphide of Trxs. These results provide a structural framework for understanding the mechanism of disulphide reduction by an iron-sulphur enzyme and describe previously unknown interaction networks for both Fdx and Trx (refs 4-6).     

亚甲基双膦酸四异丙基酯CH2[P（O）（iPrO）2]2催化合成晶体[Zn（2,2-′bipy）3]2Cl4·H2O

在亚甲基双膦酸四异丙基酯CH2[P（O）（iPrO）2]2的催化作用下,合成一种新的配合物[Zn（2,2-′bipy）3]2Cl4.H2O,并用红外光谱和X-ray单晶衍射进行了测试与表征.在反应中CH2[P（O）（iPrO）2]2并未参加配位,但却起到了催化、诱导的作用.     

Synthesis,crystal structure of a novel yttrium (Ⅲ) coordination compound supported by typical plenary Dawson cluster

Asarichanddiverseclassofinorganicclustersytems,thepolyoxometalateions,whicharecharacterizedbyfascinatingstructural,electrochemical,catalytic,manetic,medicinal,andphotophysicalproperties,havebeenfoundtobeextremelyversatileinorganicbuildingblocksinthefieldsofdesigningandassemblingmolecule-basedmaterials[1].Basedoncoordinationcapabilityofthesufaceoxygenatoms(bridgingorterminaloxygenatoms)ofthepolyoxoanions,novelcomplexeswithadiscretecluter,1D,2Dor3Dstructurescanbesynthesizedthroughmetalunitsbeing…     

新型T型簇合物[PPh4]2[WS4(CuBr)2.6]的合成与晶体结构

通过[PPh4][(mthp S)WS3](mthp=2 methyltetrahydro 2H pyran)和三当量CuBr反应合成了一个新的T型簇合物[PPh4]2[WS4(CuBr)2.6],用单晶X射线衍射方法测定了结构,其二价簇阴离子具有一个由三个铜和一个WS4单元组成的T型WS4Cu3簇结构.     

[Fe(H2O)m(OH)n]x配合物电子结构的理论研究

在B3PW91/6-31G(d, p)计算水平上，对铁离子配合物［Fe(H₂O)_m(OH)_n］^x(m+n=4; x=3+,2+,1+,0,1-)的5种可能构型进行优化计算，分析比较了优化结果的几何构型、电荷布居以及能量。计算结果表明：这5种配合物在理论上都有可能稳定存在，配体以氧原子与铁离子配位并形成四面体构型，有部分电荷从氧原子转移到铁离子，OH^-与Fe³⁺的配位作用较强。铁离子的d电子以高自旋的形式排布，形成开壳层的电子结构，其中Fe(OH)₄^-的d电子最难以发生跃迁。比较具有相同数量Fe³⁺、H₂O和OH^-的［Fe(H₂O)_m(OH)_n+jH₂O+kOH^-］体系的能量，发现随着［Fe(H₂O)_m(OH)_n］^x中OH^-数量的增加，H₂O数量的减少，体系的能量逐渐降低。所以，［Fe(OH)₄^-+6H₂O+2OH^-］体系最稳定，与布居分析中OH^-与Fe³⁺的配位作用较强的结果相一致。     

三维超分子体系[Cd(C_6H_4O_2N)_2(H_2O)_4]的合成与晶体结构

合成并测定了一种新的三维超分子体系——[Cd(C6H4O2N)2(H2O)4]的晶体结构.该晶体属于三斜晶系,Pī空间群,a=6.4461(13),b=6.9332(14),c=9.4411(19)魡,α=94.75(3)°,β=104.70(3)°,γ=112.08(3)°,V=370.63(13)魡3,μ=1.518mm-1,Z=1,M=428.67,Dc=1.921g/cm3,F(000)=214,λ(MOKα)=0.71073魡,最终偏离因子R1=0.0405,ωR2=0.1236.该超分子体系的基本结构单元[Cd(C6H4O2N)2(H2O)4]中,Cd处于八面体的中心;各个结构单元之间通过氢键相互连接,形成无限伸展、层状结构的三维超分子体系.     

[NH3（H2O）n]^-（n=2—4）团簇结构和电子结合方式研究

采用密度泛函理论B3LYP／6—311＋＋g^＊＊方法对[NH3（H2O）n]^-（n=2—4）团簇的结构和频率进行研究,从而得到[NH3（H2O）n]（n=2—4）团簇的基态结构,得到的结构与SubhaPratihar等的研究一致．同时,文章还研究了水氨团簇的电子束缚方式和偶极矩,结果表明,在n=2时,电子束缚方式为表面束缚,而在n=3,4时,既有表面束缚方式,又有内部束缚方式．     

新型离子型有机锡化合物{[Ph2Sn]2[2,6-Py(CO2)]3H2O}2-[HNEt3]+2的晶体结构研究

利用三苯基氯化锡和2,6-吡啶二甲酸在三乙胺存在下以1:1摩尔比反应,合成了离子型有机锡化合物[Ph_2Sn]_2[2,6-Py(CO_2)]_3H_2O~(2-)[HNEt_3]_2~+.通过元素分析、红外光谱和核磁共振氢谱对其结构进行了表征.用X-射线单晶衍射测定了该化合物的晶体结构.化合物的单斜晶系,空间群P2_1/n,α=1.707 3(7)nm,b=1.744 7(7)nm,c=2.433 3(10)nm,β=109.694(7)°,Z=4,V=6.824(5)nm~3,Dc=1.282 g/cm~3,μ=0.793 mm~(-1),F(000)=2 696,R_1=0.056 3,WR_2=0.1539.化合物中两个锡原子呈七配位畸变五角双锥构型.     

化合物[Co（bdpp）（NO3）2]的合成和结构

化合物[Co（bdpp）（NO3）2]（bdpp=二（3,5-二甲基吡唑）丙烷）是在乙醇溶液中通过Co（NO3）2·2HO和bdpp反应制备而成。钴离子与一个二（3,5-二甲基吡唑）丙烷和两个硝酸根离子配位形成扭曲的四面体构型。其键长和键角与同类化合物有较大差异。     

配位聚合物[Ni(4,4''''-bpy)(H2O)4]·(SO42-)·(CH3OH)·(H2O)的合成与晶体结构

通过NiSO4·6H2O与4,4'-联吡啶在H2O-CH3OH混合溶液中反应,制备了配位聚合物[Ni(4,4′-bpy)(H2O)4]·(SO42-)·(CH3OH)·(H2O),并使用X射线单晶衍射技术对其结构进行了表征.此配合物含有三种分别沿[100]、[010]、[110]方向排列的无限长链,并通过其配位水分子与位于层间位置的SO42-形成氢键而连接成为超分子结构.     

反式[FeCl2(H2O)"4]+加合瓜环的超分子结构

作为[FeCl2(H2O)4]Cl·(C36H36N24012)·4H2O加合物的一部分,反式[FeCl2(H2O)4]+的结构首次被单晶X-射线衍射分析方法加以证实.同时还用该方法解析了[FeCl2(H2O)4]Cl·(C36H36N24012)·4H2O加合物的晶体结构.     

Challenge of new biological energy resources

Hydrogenases are enzymes that can reversibly split molecular hydrogen. Study on the structure of the active site and the mechanism of catalysis has drawn great attention because the results may be useful for the design of cheap biomimetic hydrogen catalysts for fuel cells, or as model for the photoproduction of H₂. At one time the active site was generally considered to be composed of mononuclear nickel complex with ligands from the polypeptide. A breakthrough in the understanding of the structure of [NiFe] Hases occurred with the resolution crystal structure ofD. gigas [NiFe] Hases in 1995. The unexpected result challenged the previously reported spectroscopic studies and caused some academic arguments. Some methods and results used for insight into [NiFe] Hases have to be reconsidered. Different viewpoints concerning the structure of active site of [NiFe] Hases in different periods and some remaining questions will be presented.     

固氮酶反应中铁蛋白与MgATP配位的化学模拟

以[Fe_4S_4(SCH_2Ph)_4]~(-2)作为氧化态铁蛋白4Fe-4S中心的模型化合物,化学模拟研究表明,ATP能与[Fe_4S_4(SCH_2Ph)_4]~(-2)原子簇结合,促进原子簇与亚甲蓝之间的氧化还原反应速率,并敏化原子簇中的Fe(Ⅱ),使其易与亚铁螯合剂反应,用正庚烧作萃取刑,在原子簇-ATP体系没有检测到游离的HSCH_2Ph,ATP没有置换原子簇中的—SCH_2Ph,这表明作为电子活化剂的ATP可能通过其磷酸根与Fe_4S_4原子簇结合。     

Waugh结构(NH4)6[MnMo9O32]8H2O的合成与表征

利用三因素三水平正交实验确定了(NH4)6[MnMo9O32]8H2O合成的最佳条件.利用红外、紫外-可见、差热-热重和X射线对该化合物进行了表征.用循环伏安法对该化合物氧化还原的性质进行了研究.     

Na_9[Na_3{Co(H_2O)}_3(AsW_9O_(33))_2]·44H_2O的晶体结构及表征

在 p H≈ 6 .5及稀土盐的存在下 ,用 Na2 WO4 · 2 H2 O与 Na As O2 及 Co(NO3 ) 2 · 6 H2 O反应 ,得到了夹层型杂多钨酸盐 Na9[Na3 { Co(H2 O) } 3 (As W9O3 3 ) 2 ]· 44H2 O单晶 ,用 X射线单晶衍射法及元素分析确定了其结构 ,晶胞参数为 :a=1 .40 83 (6 ) nm,b=2 .3 2 4 1 (6 ) nm,c=3 .2 1 97(1 0 ) nm,α=90°,β=98.995 (6 )°,γ=90°,V=1 0 .40 8(6 ) nm3 ,Z=4,空间群 C2 /c,R1 =0 .0 6 0 4 ,w R2 =0 .0 792 (I>2 σ) .[Na3 { Co(H2 O) } 3 (As W9O3 3 ) 2 ]9-具有近似 D3 h对称性 ,Co2 +的配位数均为 5 .对题示化合物进行了 IR,UV- Vis表征 ,讨论了其形成条件     

[Ni(phen)_3]_2[NiMo_(12)P_8O_(62)H_(18)]单晶材料催化合成阿司匹林的研究

采用水热合成法制备[Ni(phen)3]2[NiMo12P8O62H18]单晶材料,通过考察反应温度、时间及催化剂用量等影响因素,确定了其催化合成阿司匹林的最佳条件为催化剂用量为0.09g,反应温度为80℃,反应时间为15min.表明[Ni(phen)3]2[NiMo12P8O62H18]单晶材料是一种催化合成阿司匹林的绿色、高效催化剂,可以为解决当前硫酸催化合成阿司匹林所产生的低效、污染及高成本的问题提供参考.