吡嗪嘧啶铱(Ⅲ)配合物的合成及其磷光材料性质

该研究采用4-苯基嘧啶(PPY)作为辅助配体合成了新型的配合物(MDPP)2Ir(Cl)PPY(MDPP为5-甲基-2,3-二苯基吡嗪).紫外-可见吸收光谱显示该配合物在475nm处有三重态的金属到配体的电荷跃迁3MLCT吸收峰;该配合物的光致发光光谱中,在558nm处有相应的3MLCT发射峰.该发射峰较用乙酰丙酮(acac)作为辅助配体得到的配合物(MDPP)2Ir(acac)蓝移了22nm,这说明PPY是一类有潜在应用价值的辅助配体,可以用于金属配合物发光颜色的调节.同时,该文还讨论了天然化合物作为有机配体的可行性.     

Organic molecules acting as templates on metal surfaces

The electronic connection of single molecules to nanoelectrodes on a surface is a basic, unsolved problem in the emerging field of molecular nanoelectronics. By means of variable temperature scanning tunneling microscopy, we show that an organic molecule (C90H98), known as the Lander, can cause the rearrangement of atoms on a Cu(110) surface. These molecules act as templates accommodating metal atoms at the step edges of the copper substrate, forming metallic nanostructures (0.75 nanometers wide and 1.85 nanometers long) that are adapted to the dimensions of the molecule.     

由乙二胺、α-萘乙酸构筑的镍(Ⅱ)配合物的合成、结构和抑菌性质研究

[目的]α-萘乙酸是一种植物生长调节剂,乙二胺是一类很好的有机配体,二者与金属离子共同反应合成金属配合物,并研究配合物的抑菌活性。[方法]通过水热合成法合成新的配合物,利用牛津杯法研究配合物的抑菌活性。[结果]成功合成了配合物[Ni(C12H9O2)2(C2H8N2)3]2,采用单晶X-射线、元素分析和FT-IR对合成配合物[Ni(C12H9O2)2(C2H8N2)3]2进行结构表征。同时,研究了该配合物的抑菌活性。[结论]该晶体属于三斜晶系,P-1空间群:a=9.145(6),b=13.146(8),c=14.385(9);α=70.120(7)°,β=74.272(7)°,γ=69.819(7)°,Z=2。Ni(II)与来自3个乙二胺分子的六个氮原子配位,形成扭曲的八面体配位构型。配合物有一定的抑菌活性。     

Ballistic electron microscopy of individual molecules

We analyzed the transport of ballistic electrons through organic molecules on uniformly flat surfaces of bismuth grown on silicon. For the fullerene C60 and for a planar organic molecule (3,4,9,10-perylene-tetracarboxylic acid dianhydride), the signals revealed characteristic submolecular patterns that indicated where ballistic transport was enhanced or attenuated. The transport was associated to specific electronic molecular states. At electron energies of a few electron volts, this "scanning near-field electron transmission microscopy" method could be applied to various adsorbates or thin layers.     

Molecular recognition and metal ion template synthesis

Methods for the design and synthesis of ligands intended to be specific for a metal ion have been a recent chemical development. This article describes how this process can be inverted so that the specifics of the coordination environment around the metal ion can be used as a template in large-scale ligand synthesis. The synthesis of macrobicyclic ligands for ferric ion has been accomplished by using active esters of catechol ligands in which catecholate coordination to iron is a prelude to the organic chemical reactions that link the coordination subunits together into one ligand system surrounding a central metal ion coordination site. The lanthanide(III) ions, which are among the most labile metal ions known, have coordination numbers of 8 or higher, and thus their encapsulation into a macrobicyclic structure is a challenging problem. Lanthanide amine complexes have been used as metal templates in the synthesis of such macrobicyclic lanthanide complexes. There is evidence that such a complex is inert to exchange in aqueous solution.     

Automated chemical synthesis of a protein growth factor for hemopoietic cells, interleukin-3

Interleukin-3 (IL-3), a protein of 140 amino acids, was chemically synthesized by means of an automated peptide synthesizer and was shown to have the biological activities attributed to native IL-3. Assays of synthetic analogues established that an amino terminal fragment has detectable IL-3 activity, but that the stable tertiary structure of the complete molecule was required for full activity. The results demonstrate that automated peptide synthesis can be applied to the study of the structure and function of proteins.     

四种紫花苜蓿的核型分析

为研究我国引进和本国育成的适于我国北方不同地区种植的四个紫花苜蓿(Medicago sativa)品种遗传基质的结构特征,对它们进行了细胞染色体的核型分析。试验利用植物压片法对四个品种:阿尔冈金(加拿大)、WL-323ML(美国)、WL-232HQ(美国)、中苜1号(中国农科院畜牧所用中外品种混合选育而成)进行了核型分析,结果表明:四个品种的染色体数目均相同(2n=32),统属于大染色体,但在核型组成上存在有一定的差异。四个品种中多数染色体为中部着丝点,核型多为对称型。但阿尔冈金、WL-232HQ及中苜1号同为2A型,它们相邻间染色体长度变化不大,进化程度相当,而WL-323ML为2C核型。第1,2对及第15,16对相邻间染色体长度变化大,余者变化小。它比前三个品种表现出更为进化的特点。阿尔冈金没有随体,WL-232HQ有1对随体,WL-323ML、中苜1号各有2对随体。     

A molecular MoS₂ edge site mimic for catalytic hydrogen generation

Inorganic solids are an important class of catalysts that often derive their activity from sparse active sites that are structurally distinct from the inactive bulk. Rationally optimizing activity is therefore beholden to the challenges in studying these active sites in molecular detail. Here, we report a molecule that mimics the structure of the proposed triangular active edge site fragments of molybdenum disulfide (MoS(2)), a widely used industrial catalyst that has shown promise as a low-cost alternative to platinum for electrocatalytic hydrogen production. By leveraging the robust coordination environment of a pentapyridyl ligand, we synthesized and structurally characterized a well-defined Mo(IV)-disulfide complex that, upon electrochemical reduction, can catalytically generate hydrogen from acidic organic media as well as from acidic water.     

单技术修复复合污染土壤的初步研究

利用高效液相色谱法比较研究了水相中阴、阳、非表面活性剂和环境友好的有机溶剂乳酸乙酯对芘溶解度的影响。结果发现，表面活性剂的增溶效果比乳酸乙酯强。为了确定能否用配体和有机溶剂同时修复土壤复合污染，还研究了有机溶剂跟配体共同作用对芘溶解效果的影响，结果在乳酸乙酯体系中加入EDDS、EDTA、NTA配体增加了芘的增溶效果。结合已有研究表明的乳酸乙酯可以增加配体对重金属的洗脱效率的结论，理论上在配体中加入有机溶剂可以对土壤进行复合修复。通过在模拟污染土壤中研究各种不同组合对重金属和有机物的共同洗脱效果发现，乳酸乙酯跟配体的组合对土壤复合修复达到了相当好的效果，由此可为土壤复合污染提供一个生态安全的修复途径。     

Activation of alkanes with organotransition metal complexes

Alkanes, although plentiful enough to be considered for use as feedstocks in large-scale chemical processes, are so unreactive that relatively few chemical reagents have been developed to convert them to molecules having useful functional groups. However, a recently synthesized iridium (lr) complex successfully converts alkanes into hydridoalkylmetal complexes (M + R-H --> R-M-H). This is a dihydride having the formula Cp(*)(L)lrH(2), where Cp(*) and L are abbreviations for the ligands (CH(3))(5)C(5) and (CH(3))(3)P, respectively. Irradiation with ultraviolet light causes the dihydride to lose H(2), generating the reactive intermediate Cp(*)lrL. This intermediate reacts rapidly with C-H bonds in every molecule so far tested (including alkanes) and leads to hydridoalkyliridium complexes Cp(*)(L)lr(R)(H). Evidence has been obtained that this C-H insertion, or oxidative addition, reaction proceeds through a simple three-center transition state and does not involve organic free radicals as intermediates. Thus the intermediate Cp(*)lrL reacts most rapidly with C-H bonds having relatively high bond energies, such as those at primary carbon centers, in small organic rings, and in aromatic rings. This contrasts directly with the type of hydrogen-abstraction selectivity that is characteristic of organic radicals. The hydridoalkyliridium products of the insertion reactions can be converted into functionalized organic molecules-alkyl halides-by treatment with mercuric chloride followed by halogens. Expulsion (reductive elimination) of the hydrocarbon from the hydridoalkyliridium complexes can be induced by Lewis acids or heat, regenerating the reactive intermediate Cp(*)lrL. Oxidative addition of the corresponding rhodium complexes Cp(*)RhL to alkane C-H bonds has also been observed, although the products formed in this case are much less stable and undergo reductive elimination at -20 degrees C. These and other recent observations provide an incentive for reexamining the factors that have been assumed to control the rate of reaction of transition metal complexes with C-H bonds-notably the need for electron-rich metals and the proximity of reacting centers.     

Solar Energy Conversion by Water Photodissociation: Transition metal complexes can provide low-energy cyclic systems for catalytic photodissociation of water

The basic concepts for direct and catalyzed photodissociation of water have been summarized. Water dissociation in closed-cycle processes based on endothermic photochemical reactions offers a potential solution to the solar energy conversion problem. Transition metal complexes, whose excited state chemistry is extremely rich (23, 24) although mostly unexplored, are, in principle, suitable "catalysts" for cycles of this type. The most interesting cycles are those involving metal hydrido complexes or binuclear complexes in which the two metal atoms are bound into a macrocyclic ligand. Systematic investigations of the photochemistry of transition metal complexes with the aim of designing suitable systems for solar energy conversion have long-range promise and merit further consideration.     

混合络合物的形成及生物学意义

自然界特别是在生物体系中广泛地存在着混合型络合物。它的形成可以是一步同时生成或逐步生成,也可以是由单一型络合物混合生成。混合络合物的稳定性是由如下因素所决定的,即:统计效应,静电效应,共价键性,立体效应和配体的合作效应。在生物体内,混合络合物的形成涉及到:生物分子的稳定化和三维构象的稳定化,金属离子和配体分子的分布和运转,某些金属酶的催化作用(如脱羧酶、水解酶,羰基水化酶,碳酸酐酶等)及生物固氮等等问题。     

A three-dimensional synthetic metallic crystal composed of single-component molecules

Molecular metals normally require charge transfer between two different chemical species. We prepared crystals of [Ni(tmdt)2] (tmdt, trimethylenetetrathiafulvalenedithiolate) and carried out crystal structure analyses and resistivity measurements. The analyses and measurements revealed that these single-component molecular crystals are metallic from room temperature down to 0.6 kelvin. Ab initio molecular orbital calculations suggested that pi molecular orbitals form conduction bands. The compact molecular arrangement, intermolecular overlap integrals of the highest occupied and lowest unoccupied molecular orbitals, and tight-binding electronic band structure calculation revealed that [Ni(tmdt)2] is a three-dimensional synthetic metal composed of planar molecules.     

Molecular rulers for scaling down nanostructures

A method of constructing <30-nanometer structures in close proximity with precise spacings is presented that uses the step-by-step application of organic molecules and metal ions as size-controlled resists on predetermined patterns, such as those formed by electron-beam lithography. The organic molecules serve as a ruler for scaling down a larger "parent" structure. After metal deposition and lift-off of the organic multilayer resist, an isolated smaller structure remains on the surface. This approach is used to form thin parallel wires (15 to 70 nanometers in width and 1 micrometer long) of controlled thickness and spacing. The structures obtained were imaged with field emission scanning electron microscopy. A variety of nanostructures could be scaled down, including structures with hollow patterns.     

有机物料及其用量对生菜生长与Pb含量的影响

为了降低叶菜中重金属Pb的含量,选择有机肥、猪粪、牛粪、鸡粪和花生麸5种有机物料为材料,分别以0.5%、1%、2%、4%4个水平的用量施入重金属污染土壤,通过种植3茬生菜(Lactuca sativa L.)的盆栽试验研究有机物料对重金属污染土壤上生菜生长及其Pb含量的影响。结果表明,与对照相比,有机物料利于生菜生长,有提高生菜生物量的趋势;大部分有机物料处理没有显著影响生菜地上部分的Pb含量;5种有机物料中,仅牛粪有提高生菜地上部Pb含量的趋势;生菜Pb含量平均值高低的顺序为牛粪>鸡粪>花生麸>有机肥>猪粪,但不同有机物料之间没有显著差异。与对照相比,大部分处理没有显著影响土壤的DTPA-Pb含量,初步揭示了供试有机物料没有显著影响生菜地上部Pb含量的原因。     

Microbial factor-mediated development in a host-bacterial mutualism

Tracheal cytotoxin (TCT), a fragment of the bacterial surface molecule peptidoglycan (PGN), is the factor responsible for the extensive tissue damage characteristic of whooping cough and gonorrhea infections. Here, we report that Vibrio fischeri also releases TCT, which acts in synergy with lipopolysaccharide (LPS) to trigger tissue development in its mutualistic symbiosis with the squid Euprymna scolopes. As components of PGN and LPS have commonly been linked with pathogenesis in animals, these findings demonstrate that host interpretation of these bacterial signal molecules is context dependent. Therefore, such differences in interpretation can lead to either inflammation and disease or to the establishment of a mutually beneficial animal-microbe association.     

Nonphotographic alpha autoradiography and neutron-induced autoradiography

With a new combination of two techniques, (i) alpha-particle or fission fragment registration in thin polymer foils by etching and (ii) automatic counting and magnification of the etched perforations by local evaporation of a thin metal layer with an electric spark, the sensitivity of conventional photographic methods for determining quantity and spatial distribution of alpha emitters, fissile materials, and of elements undergoing (n, alpha) reactions can be drastically improved, without need for darkroom processing and microscopic evaluation.     

不同调酸剂对种植玉米红壤微生物群落的影响

为研究红壤微生物丰度和群落组成对不同调酸剂的响应,分析影响碳/氮关键代谢过程微生物的变化,通过盆栽实验,设置不施肥（CK）、钙镁复合剂（L）、钙镁复合剂配施猪粪（ML）和钙镁复合剂配施秸秆（SL）4个处理,采用宏基因组测序技术,分析土壤细菌、真菌和古菌以及碳/氮代谢关键过程微生物。结果表明：L、ML和SL处理显著提高土壤pH值和交换性钙/镁,显著降低土壤交换性酸。调酸剂增加了细菌优势菌中的变形菌门相对丰度,降低了绿弯菌门和酸杆菌门相对丰度;降低了真菌优势菌中的毛霉菌门相对丰度;增加了古菌优势菌中的广古菌门和深古菌门的相对丰度,降低了奇古菌门的相对丰度。冗余分析结果显示,速效钾是影响土壤细菌和真菌群落结构的主要环境因子,土壤pH和有机碳是影响土壤真菌和古菌群落结构组成的关键因子。碳代谢过程的贡献度方面,变形菌门的贡献度在SL处理中最高,放线菌门和芽单胞菌门的贡献度在ML处理中最高。氮代谢过程中,各处理绿弯菌门对硝化作用的贡献率均超过80%。调酸降低了绿弯菌门和酸杆菌门在反硝化与硝酸盐异化还原过程中的贡献度,L与SL处理的变形菌门贡献度低于ML处理,而ML处理的放线菌门贡献度高于L与SL处...     

Recapitulation of IVIG anti-inflammatory activity with a recombinant IgG Fc

It is well established that high doses of monomeric immunoglobulin G (IgG) purified from pooled human plasma [intravenous immunoglobulin (IVIG)] confer anti-inflammatory activity in a variety of autoimmune settings. However, exactly how those effects are mediated is not clear because of the heterogeneity of IVIG. Recent studies have demonstrated that the anti-inflammatory activity of IgG is completely dependent on sialylation of the N-linked glycan of the IgG Fc fragment. Here we determine the precise glycan requirements for this anti-inflammatory activity, allowing us to engineer an appropriate IgG1 Fc fragment, and thus generate a fully recombinant, sialylated IgG1 Fc with greatly enhanced potency. This therapeutic molecule precisely defines the biologically active component of IVIG and helps guide development of an IVIG replacement with improved activity and availability.