Structure of the hydrophilic domain of respiratory complex I from Thermus thermophilus

Respiratory complex I plays a central role in cellular energy production in bacteria and mitochondria. Its dysfunction is implicated in many human neurodegenerative diseases, as well as in aging. The crystal structure of the hydrophilic domain (peripheral arm) of complex I from Thermus thermophilus has been solved at 3.3 angstrom resolution. This subcomplex consists of eight subunits and contains all the redox centers of the enzyme, including nine iron-sulfur clusters. The primary electron acceptor, flavin-mononucleotide, is within electron transfer distance of cluster N3, leading to the main redox pathway, and of the distal cluster N1a, a possible antioxidant. The structure reveals new aspects of the mechanism and evolution of the enzyme. The terminal cluster N2 is coordinated, uniquely, by two consecutive cysteines. The novel subunit Nqo15 has a similar fold to the mitochondrial iron chaperone frataxin, and it may be involved in iron-sulfur cluster regeneration in the complex.     

固氮施氏假单胞菌电子传递复合体rnf基因簇的功能鉴定

能量供应是限制生物固氮效率的重要因素,电子传递复合体是生物固氮过程中能量产生的重要组成部分。基因组分析表明,在联合固氮菌施氏假单胞菌A1501基因组中存在两套编码电子传递复合体rnf,分别为基因簇rnf1和rnf2,其中rnf1位于固氮基因岛上,rnf2基因簇位于核心基因组上。为了明确两套电子传递体在生物固氮过程中的功能,分别构建了rnf1和rnf2基因簇的突变株并测定了相关表型。结果发现,在基本培养基中两个基因簇的突变都不影响菌体生长,可能相互之间存在着功能互补;固氮酶活性测定结果表明,位于固氮基因岛中的rnf1基因簇缺失造成固氮酶活下降80%以上,而rnf2基因簇的缺失对酶活无显著影响。进一步采用启动子-lacZ融合表达策略探究了基因簇rnf1对固氮酶结构基因nifH转录的影响,发现rnf1极性突变株中nifH的启动子转录活性仅为野生型的17.59%,推测rnf1缺失造成了固氮条件下能量产生匮乏,胞内碳氮比失衡,进而造成固氮系统表达受抑制。     

A Ni-Fe-Cu center in a bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase

A metallocofactor containing iron, sulfur, copper, and nickel has been discovered in the enzyme carbon monoxide dehydrogenase/acetyl-CoA (coenzyme A) synthase from Moorella thermoacetica (f. Clostridium thermoaceticum). Our structure at 2.2 angstrom resolution reveals that the cofactor responsible for the assembly of acetyl-CoA contains a [Fe4S4] cubane bridged to a copper-nickel binuclear site. The presence of these three metals together in one cluster was unanticipated and suggests a newly discovered role for copper in biology. The different active sites of this bifunctional enzyme complex are connected via a channel, 138 angstroms long, that provides a conduit for carbon monoxide generated at the C-cluster on one subunit to be incorporated into acetyl-CoA at the A-cluster on the other subunit.     

烟草数量性状遗传距离的初步研究(云南省科委应用基础研究基金资助课题)

利用多元分析法测定了25个烟草品种7个农艺性状的主成分遗传距离,并据之进行了聚类分析。在5.5聚类水平下,25个品种划归为6类,各类间性状差异明显,类内相似,这种分类在育种中可用作亲本选配,结果表明遗传距离是度量烟草品种遗传差异的一个有效参数,值得进一步研究。     

烟草数量性状遗传距离的初步研究(云南省科委应用基础研究基金资助课题)

 利用多元分析法测定了25个烟草品种7个农艺性状的主成分遗传距离,并据之进行了聚类分析。在5.5聚类水平下,25个品种划归为6类,各类间性状差异明显,类内相似,这种分类在育种中可用作亲本选配,结果表明遗传距离是度量烟草品种遗传差异的一个有效参数,值得进一步研究。     

The origin of galaxies and clusters of galaxies

Debate on how galaxies and clusters of galaxies formed has reached an interesting stage at which one can find arguments for quite different scenarios. The galaxy distribution has a complex "frothy" character that could be the fossil of a network of protoclusters or pancakes that produced galaxies. However, there are galaxies like our own that seem never to have been in a protocluster but are physically similar to the galaxies in dense clusters. Some clues to be assessed in resolving this dilemma are the possible existence of galaxy filaments, the relative ages of galaxies and clusters of galaxies, and the continuity between cluster and field galaxies and between galaxies and clusters of galaxies.     

Stormy weather in galaxy clusters

Recent x-ray, optical, and radio observations coupled with particle and gas dynamics numerical simulations reveal an unexpectedly complex environment within clusters of galaxies, driven by ongoing accretion of matter from large-scale supercluster filaments. Mergers between clusters and continuous infall of dark matter and baryons from the cluster periphery produce long-lived "stormy weather" within the gaseous cluster atmosphere-shocks, turbulence, and winds of more than 1000 kilometers per second. This weather may be responsible for shaping a rich variety of extended radio sources, which in turn act as "barometers" and "anemometers" of cluster weather.     

Quantum solvation of carbonyl sulfide with helium atoms

High-resolution infrared and microwave spectra of He(N)-carbonyl sulfide (He(N)-OCS) clusters with N ranging from 2 to 8 have been detected and unambiguously assigned. The spectra show the formation of a solvation layer beginning with an equatorial "donut" of five helium atoms around the OCS molecule. The cluster moment of inertia increases as a function of N and overshoots the liquid droplet limit for N > 5, implying that even atoms in the first solvation shell are decoupled from the OCS rotation in helium nanodroplets. To the extent that this is due to superfluidity, the results directly explore the microscopic evolution of a phenomenon that is formally macroscopic in nature.     

降水污染的簇分析

运用簇分析区分不同时间段降水的化学变化,将单个降水事件作为变量来分析,每次降水测量的9项主要离子指定为簇分析的观察值,簇分析完成后,保留6类簇作为描述对象.根据簇中各离子浓度的高低,将各簇概括为:氢离子簇(簇1);无特征离子簇(簇2);氯离子、钠离子簇(簇3);硫酸根、铵根离子簇(簇4);钙、镁离子簇(簇5);硝酸根、钾离子簇(簇6).显然,簇1属酸性降水簇,簇3是海洋型降水簇,簇2、5为中间过渡型,簇4、6为高离子浓度簇,强酸性降水与高离子浓度降水并不属于同一类,降水的酸性与降水中的碱性组分密切相关,降水的酸度仅当NH4+、Ca2+离子浓度尤其是NH4+离子浓度较低时才表现为强酸性.由东北季风气流和锋面系统控制的降水(簇1、2、3)是污染物经较长距离迁移造成的强酸性降水,簇4、簇5、簇6的降水受局地污染源影响,所含的离子浓度较高.     

苦瓜遗传多样性的形态学性状聚类分析

对苦瓜的33个种质资源的植株、果实和种子等28类形态学性状进行聚类分析,结果表明:供试资源可划分为3个组群,即野生型组群(组群I)、密瘤小果型组群(组群II)及长大果型组群(组群III);其中组群III又可以进一步分为3个亚组群。各组群间存在明显的地域性差异,野生型及密瘤小果型主要分布于东南亚及印度、孟加拉、斯里兰卡等地区,长大果型则主要分布在中国大陆及泰国。各地域范围内的种质遗传距离较近,而地域间的种质遗传距离较远,特别是中国大陆的苦瓜种质与发源地印度的热带区域和东南亚热带地区的种质资源间有很远的遗传距离,因此,通过从东南亚及印度、孟加拉等区域引进苦瓜种质资源是拓宽我国苦瓜资源遗传背景,在育种工作上获取突破性进展的快捷有效途径。     

两个溶藻弧菌胞外多糖合成基因簇的生物信息学分析

溶藻弧菌是我国南方海水养殖最重要的病原菌之一。胞外多糖(EPSs)是细菌产生的一类具有复杂结构的多糖类物质,影响其致病性和环境适应力。基因组分析发现溶藻弧菌ZJ-51存在4个与胞外多糖合成有关的基因簇,笔者对其中2个基因簇CPS1357和CPS4543进行了生物信息学分析和实验验证。结果表明,基因簇CPS4543编码3个多糖外膜转运体系的同源蛋白Wza-Wzb-Wzc,而CPS1357编码的17个蛋白与多糖合成、转运以及调控有关。但通过染色实验、菌落形态观察和运动性分析证实这2个基因簇的缺失并不影响EPSs的合成、生物膜的形成、菌落形态及运动性。这可能是这2个基因簇在当前测试条件下受到抑制或需要特殊的环境因子诱导表达,对溶藻弧菌EPSs合成调控机制的研究,能更好地了解该病原菌在环境中的适应性。     

Crystal structure of biotin synthase, an S-adenosylmethionine-dependent radical enzyme

The crystal structure of biotin synthase from Escherichia coli in complex with S-adenosyl-L-methionine and dethiobiotin has been determined to 3.4 angstrom resolution. This structure addresses how "AdoMet radical" or "radical SAM" enzymes use Fe4S4 clusters and S-adenosyl-L-methionine to generate organic radicals. Biotin synthase catalyzes the radical-mediated insertion of sulfur into dethiobiotin to form biotin. The structure places the substrates between the Fe4S4 cluster, essential for radical generation, and the Fe2S2 cluster, postulated to be the source of sulfur, with both clusters in unprecedented coordination environments.     

The interface between the biological and inorganic worlds: iron-sulfur metalloclusters

Complex iron-sulfur metalloclusters form the active sites of the enzymes that catalyze redox transformations of N2, CO, and H2, which are likely components of Earth's primordial atmosphere. Although these centers reflect the organizational principles of simpler iron-sulfur clusters, they exhibit extensive elaborations that confer specific ligand-binding and catalytic properties. These changes were probably achieved through evolutionary processes, including the fusion of small clusters, the addition of new metals, and the development of cluster assembly pathways, driven by selective pressures resulting from changes in the chemical composition of the biosphere.     

产业集群对漳浦城镇化的影响研究

城镇化是推动我国经济持续发展的最大动力,而产业集群的发展加快了城镇化所需的各种要素的形成及发展速度。对漳浦食品产业集群影响城镇化发展的相关问题进行分析,并从产业集群的信息共享效应、乘数效应、规模经济和外部经济优势三方面分析了产业集群对城镇化发展的促进作用。同时通过实证分析,验证了漳浦食品产业集群对城镇化发展的作用,并且两者相互促进、共同发展。最后,就如何提高产业集群对城镇化的推动作用提出以下建议:完善和统一要素市场,完善城镇基础设施,加强政府服务职能,通过发展优势产业发挥集群效应。     

湖南生猪生产波动影响因素的实证分析及政策建议

本文在明确农业产业集群含义的基础上,通过对辽宁省农业产业集群的个案调查研究,总结出农业产业集群有三种成长模式,即基础推动型农业产业集群,企业带动型农业产业集群和市场导向型农业产业集群。这三种成长模式只是广义上的农业产业集群向严格意义的农业产业集群发展中形成的不同路径方式。针对不同成长模式存在的问题,提出相应的对策建议。不同地区在发展本地农业产业集群时,可以依据自身优势,有不同的模式选择。     

陕西省农家小麦品种主要加工品质特性及其聚类分析

研究了测定了陕西省１３１个主要农家小麦品种的粗蛋白含量,籽粒硬度和全麦粉ＳＤＳ－沉淀值,并根据这３个品质性状,利用离差平方和法对供试品种进行了总聚类和分区聚类分析。总聚类分析中,供试品种被聚为４类。     

Antiferromagnetic Ordering and Paramagnetic Behavior of Ferromagnetic Cu6 and Cu18 Clusters in BaCuO2+x

Magnetization and neutron diffraction measurements on polycrystalline BaCuO2+x revealed a combination of magnetic behaviors. The Cu(6) ring clusters and Cu(18) sphere clusters in this compound had ferromagnetic ground states with large spins 3 and 9, respectively. The Cu(6) rings ordered antiferromagnetically below the Néel temperature T(N) = 15 +/- 0.5 kelvin, whereas the Cu(18) spheres remained paramagnetic down to 2 kelvin. The ordered moment below T(N) was 0.89(5) Bohr magnetons per Cu in the Cu(6) rings, demonstrating that quantum fluctuation effects are small in these atomic clusters. The Cu(18) clusters are predicted to exhibit ferromagnetic intercluster order below about 1 kelvin.     

农产品监测预警模型集群构建理论方法与应用

【目的】农产品供给与需求的准确分析测定,是农业监测预警能力提升的重要表现。构建产品多品种多环节模型集群理论方法,可高效解决单一环节或单一模型难以解决的分析技术难题。【方法】在农产品供需的重要要素即生产量、消费量、贸易量、价格等分析预测过程中,针对农产品品种间关联性强,自然、社会、经济诸多影响因素纠缠,模型多变量强耦合、非线性、参数时变的特点,提出多品种农产品“因素分类解耦、参数转用适配”方法,以构建多时空维度的监测预警模型集群。【结果】利用“因素分类解耦、参数转用适配”技术方法,研究构建了不同农产品的生产类、消费类、贸易类、价格类的模型集群。这些模型集群可用于对不同时空维度的水稻、玉米、小麦、肉类等主要农产品供需的长中短期的分析预测,支撑形成了农业展望中的主要农产品平衡表,其中主要农产品全国年度生产量6年平均预测精度高于97%。【结论】研究提出的农产品监测预警模型集群构建理论及其方法,有效提升了农产品多品种模型集群的求解效率和准确率,增强了农产品供需分析预测的系统性与智能性,为系统揭示农产品复杂的时空供需变化特征、促进农产品市场调控科学性和可预见性,提供了新技术方法。     

MMS19 links cytoplasmic iron-sulfur cluster assembly to DNA metabolism

The function of many DNA metabolism proteins depends on their ability to coordinate an iron-sulfur (Fe-S) cluster. Biogenesis of Fe-S proteins is a multistep process that takes place in mitochondria and the cytoplasm, but how it is linked to nuclear Fe-S proteins is not known. Here, we demonstrate that MMS19 forms a complex with the cytoplasmic Fe-S assembly (CIA) proteins CIAO1, IOP1, and MIP18. Cytoplasmic MMS19 also binds to multiple nuclear Fe-S proteins involved in DNA metabolism. In the absence of MMS19, a failure to transfer Fe-S clusters to target proteins is associated with Fe-S protein instability and preimplantation death of mice in which Mms19 has been knocked out. We propose that MMS19 functions as a platform to facilitate Fe-S cluster transfer to proteins critical for DNA replication and repair.