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  1. 卓越的电子给体 ELECTRON DONOR PAR EXCELLENCE
  2. SARS Researchers in China Use SGI Technologies to Search for Genomic

美国化学会《化学与工程新闻》作为2002年12月9日标题新闻报道
http://pubs.acs.org/email/cen/html/121002115047.html

卓越的电子给体
--Ditungsten桨轮式复合物比铯更容易离子化

      由于铯原子长时间保持着离子化能为3.89eV的最低记录,因而具有最易离子化的元素的特点。很长时间以来,没有一个完整的分子能与之竞争。
      但是,现在发现了一个具有明显低离子化能(目前为3.51eV)的稳定分子。这个分子及它的同类成为一种强大的新的还原剂,可能引发全新的化学转换和行为。[Science, 298, 1971(2002)]
      这一发现源于几年前德克萨斯大学的F. Albert Cotton教授和Carlos A. Murillo副教授的一项研究。这个研究包括一个双金属桨轮状复合物,它有一个由金属-金属多重键形成了一个带4片叶片(阴离子配体桥联两个金属原子)的轮状的轴。
双金属桨轮状复合物       几年前,Cotton,Murillo及同事们发现了一个有前景的称之为hpp(六氢嘧啶基嘧啶阴离子,the anion of a hexahydropyrimidopyrimidine)的新桥联配体。该桥联配体在稳定高氧化态双金属体系方面强于其他配体。换言之,强碱性的hpp配体更容易氧化一些化合物,例如四键的Mo24+单元。实际上,只是将Mo2(hpp)4溶解于含氯的溶剂,例如CH2Cl2,就可以形成Mo25+化合物-即产生一定量的Mo2(hpp)4Cl。在额外氧化剂的帮助下,双金属单元可以更进一步氧化成Mo26+。Murillo说,这很不寻常。       
      由于双钨化合物比双钼化合物更易氧化,德克萨斯的研究者也制备了W2(hpp)4。对于这个化合物,他们在Science上报道说,“它如此容易氧化,以至于可以直接从含氯烷烃中得到W2(hpp)4Cl2。”
      Cotton教授请他在亚利桑那大学的同事Dennis L. Lichtenberger对dimetal hpp复合物做了一个气相的光电子谱实验。光谱的实验结果表明W2(hpp)4在3.51eV时开始电离。“这太令人惊奇了。”Lichtenberger说道。“我从来没有期望有什么在试验瓶里的分子能有如此低的电离能。”dimolybdenum及其类似物也有相对低的电离能,尽管超过了铯和一个已知的有机金属分子的电离能。
      这个实验与中国科学院上海药物所的化学家顾建德教授的理论计算一起表明在电离过程中,有一个电子从金属-金属四重键的成键轨道被电离。“四重键的成键轨道与填充轨道间很强的相互作用,导致了极低电离能。”研究人员解释道。
      Ohio州立大学的化学教授Malcolm H. Chisholm把这个发现称为“令人惊奇的”和“十分了不起的”。他相信hpp的复合物有能力成为“关键的非配位还原剂”,并且是通过与传统反应机理不同的方式来反应的。
      Cotton和Murillo表明dimetal hpp复合物很容易转移电子给电子受体,比如7,7,8,8-四氰基对苯二酚二甲基(TCNQ)和buckminsterfullerene化合物,以得到相应的负离子或二价的负离子。
      他们的研究表明通过化学改造hpp配体,研究人员可以得到更低电离能的分子。

[原文]American Chemical Society - Chemical and Engineering News in Dec.9, 2002 Headline
                    ELECTRON DONOR PAR EXCELLENCE
Ditungsten paddlewheel complex bests cesium in ease of ionization

http://www.sgi.com/newsroom/press_releases/2003/may/sars.html

SARS Researchers in China Use SGI Technologies to Search for Genomic Clues and Anti-SARS Drugs

Beijing Genomics Institute and Shanghai Institute of Materia Medica Make Significant Progress on SARS Research Using SGI Origin Family Servers

Mountain View, Calif. (May 20, 2003)--Separated by 676 miles, two key research institutes at ground zero of the severe acute respiratory syndrome (SARS) epidemic are conducting breakthrough research into this mysterious disease, using SGI® servers to advance their important work. The Beijing Genomics Institute (BGI) is identifying the genomic basis for SARS in its many variations, while the Shanghai Institute of Materia Medica (SIMM) is pursuing an effective pharmaceutical vaccine or cure. Currently, there is no rapid test available to confirm diagnosis of this newly characterized respiratory illness in a timely manner, and there is no known effective treatment or cure.

At SIMM, researchers are engaged in urgent SARS-related drug discovery research that encompasses:

  • Analyzing the genomic sequence of the virus thought to cause SARS and identifying important proteins that may be involved in the infection
  • Predicting alterations in the identified proteins expected in this mutable virus
  • Constructing 3D models of these proteins and performing virtual screenings to discover active compounds with the potential to combat SARS
  • Synthesizing and screening candidate drugs
  • Performing anti-SARS tests
To date, SIMM researchers have created 3D models of several SARS proteins and have already performed several virtual screenings utilizing numerous databases of potential drug compounds.

The backbone of this research is a 64-processor SGI® Origin® 3800 supercomputer, an additional four-processor SGI® Origin® 3200 server and 15 SGI graphics workstations used to model and virtually screen several million structures with the goal of developing a new compound to combat the SARS virus. The Origin® server handles data-intensive virtual screening tasks and the storage of many huge chemical databases, both of which require the shared memory and scalability of the Origin family's OpenGL® application programming interface and NUMAflexTM technologies. To address the SARS virus' characteristic mutation, the supercomputer is being used to map mutation sites and to create data sets pinpointing the structure of mutant proteins. Researchers utilize their SGI graphics workstations to create 3D models of these protein structures and to analyze the virtual screening results in real time.

SIMM, a branch of the Chinese Academy of Sciences, focuses on discovering new drugs and drug candidates through an interdisciplinary mix of such fields as biology, computer science, molecular biology, informatics and computer-aided drug design.

"Our approach to the pressing need for SARS research is high-throughput virtual screening integrated with chemistry and pharmacology," explains Dr. Jiang Hualiang, head of a key SARS research team at SIMM. "We are hoping within the next three months to find strong candidate compounds that may potentially kill the SARS virus. The SGI Origin supercomputer is incredibly powerful and stable, a must for such tasks as parallel computation, which is critical in reducing screening time. Our SGI workstations provide crucial visualization capabilities for constructing 3D models."

The esteemed Beijing Genomics Institute, a member of the International Human Genome Project Consortium best known for its important work in the sequencing of the rice genome, was founded in 1999. BGI researchers are fast at work sequencing 100 isolates of SARS in order to study the multitude of variations of this unusually mutative virus. In addition, diagnostic kits, vaccine and drug solutions are under rapid development.

BGI, the largest nonprofit genomics research institute in the Asia Pacific region and the third-largest genomics research center in the world, relies on two 32-processor SGI® Origin® 3000 supercomputers, a 5TB SGI® TP9100 Fibre Channel storage system and several Silicon Graphics® O2® graphics systems. These technologies are being used for such vital tasks as the modeling of both the genomic basis of SARS and SARS-related protein sequences, along with a variety of intensive computational applications.

"The institute's threefold mission is to sequence genomes of all kinds, particularly agricultural-related genomes, to advance the study of DNA, RNA, protein structures and bioinformatics and to conduct research on human health-related issues, including not only the current SARS initiative but also genotyping and antibody-antigen studies," says Dr. Wang Jun, who heads the BGI's Beijing campus and its bioinformatics department. "All of these goals present huge high-performance computing demands, especially in the areas of comparative studies and genome-related analysis. Our SGI infrastructure uniquely meets our large and very complex HPC and graphics challenges."

"We are honored that SIMM and BGI, two world-renowned institutes conducting valuable research into a devastating disease, are using SGI products to accelerate insight and discovery," said SGI CEO and Chairman Bob Bishop. "Many other advanced laboratories are doing the same, because SGI understands the urgency of leading-edge science and of the breakthrough thinking that is needed to succeed."




药物发现与设计中心(DDDC),
上海药物研究所(SIMM), 中国科学院(CAS)