THE PRIMARY STRUCTURE OF ARROWHEAD PROTEINASE INHIBITOR

After the reduction and carboxymethylation of disulfide bonds, arrowhead proteinase inhibitors A and B were cleaved either by proteinases or by cyanogen bromide, the fractionated and purified peptides were then subjected to sequencing by a gas phase automatic sequencer, the primary structures were completed by the alignment of the peptides sequenced with overlapping peptides. Both inhibitors A and B consist of 150 amino acid residues with three pairs of disulfide bonds, share 90% homology in structure, and are markedly different from all other Ser proteinase inhibitors so far known. Hence, the arrowhead inhibitor may belong to a new inhibitor family. Based on their structure characteristics, it was deduced that both their two reactive sites might be located in the positions of Lys-Ser (45-46) and Arg-Tyr-Lys (77-79), respectively. Among 13 mutated residues in inhibitors A and B, the substitution of residue Arg in position 87 of inhibitor B for residue Leu in A might be the main cause of leading to diffe     

Protein PTMs: post‐translational modifications or pesky trouble makers?

Analysis of protein post‐translational modifications using mass spectrometry is an intensive area of proteomic research. This perspective discusses the current state of the field with respect to what can be achieved, the challenges encountered, most notably with modification site assignment, the reliability of the published results, consequences of unreliable data and what is needed to be done to improve the situation. Copyright © 2010 John Wiley & Sons, Ltd.     

纳米颗粒对沸腾活化核心密度的影响

根据实验所得沸腾曲线,对纳米颗粒悬浮液进行稳态数值模拟,计算了不同过热度下活化核心的密度.计算结果表明一对于不同浓度的纳米颗粒悬浮液,在考虑了其物性变化对沸腾传热的影响外,颗粒的加入对活化核心密度产生的影响是主要的因素,并且影响效果随颗粒浓度的变化不呈单向趋势.     

Theoretical study on the reactive sites and intramolecular interactions in taxol and its four analogues

A density‐functional study of the paclitaxel (Taxol) molecule and its four analogues has been performed. The theory of Bader's atoms in molecules (AIM) was applied to examine the electronic structure of these molecules at their ground state. Topological analysis reveals that the esterification of hydroxyl group attached to the oxetane ring results in great change of conformation of the taxane ring, and thus is responsible for bioactivity of the oxetane oxygen atom. It was found that there exists some intramolecular interactions in the molecule, including normal hydrogen bonds (HBs) and double HBs. Visualization of the molecule shows that the central bodies (the four fused rings) of the molecules are wrapped by the intramolecular interactions. It is supposed that these intramolecular interactions lower the aqueous solubility and protect the flexible oxetane ring, which is regarded as the dominating bioactivity site of the drug, from being opened. Our results provide an extended and consistent set of data to gauge classical force fields in view of the atomistic investigations of the interaction of the bioactive molecules. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Enzyme active sites: bioinformatics,architecture, and mechanisms of action

A comparative analysis of the amino acid sequences of some enzymes which comprise superfamilies of enzymes belonging to different classes was carried out. Based on the amino acid sequence alignment for enzymes belonging to different classes with the use of the information entropy as a criterion, the amino acid residues involved in the catalytic portion of the active site are demonstrated to be most conservative. The rating scale for conservativeness of amino acids in enzymes is created. Glycine and aspartic acid are the most commonly occurring conservative amino acids essential for the catalysis. The role of aspartic acid and histidine in the mechanism of molecule activation in the catalytic site is considered using hydrolases as examples. The role of glycine, proline, and cysteine in the structural organization of the active sites is discussed.     

Biological X‐ray absorption spectroscopy and metalloproteomics

In the past seven years the size of the known protein sequence universe has been rapidly expanding. At present, more then five million entries are included in the UniProtKB/TrEMBL protein database. In this context, a retrospective evaluation of recent X‐ray absorption studies is undertaken to assess its potential role in metalloproteomics. Metalloproteomics is the structural and functional characterization of metal‐binding proteins. This is a new area of active research which has particular relevance to biology and for which X‐ray absorption spectroscopy is ideally suited. In the last three years, biological X‐ray absorption spectroscopy (BioXAS) has been included among the techniques used in post‐genomics initiatives for metalloprotein characterization. The emphasis of this review is on the progress in BioXAS that has emerged from recent meetings in 2007–2008. Developments required to enable BioXAS studies to better contribute to metalloproteomics throughput are also discussed. Overall, this paper suggests that X‐ray absorption spectroscopy could have a higher impact on metalloproteomics, contributing significantly to the understanding of metal site structures and of reaction mechanisms for metalloproteins.     

AHP在建设用地项目选址中的应用

本文利用 AHP方法有效地解决了建设用地项目选址中的实际问题 ,为建设项目选址决策提供了科学的依据。     

镍酶及其模型化合物的研究*

本文介绍5种镍酶即尿酶、镍氢化酶、一氧化碳脱氢酶／乙酰辅酶A合成酶、甲基辅酶M还原酶和超氧化歧化酶的结构和功能及其模型化合物的最新研究进展。     

Cd(Ⅱ)和ATP的结合位点的NMR研究

用NMR方法研究了金属镉离子在ATP(嘌呤三磷酸腺苷)上的配位点.测量了不同pH值时由于Cd²⁺的存在而引起的¹H,¹⁵N及³¹P的化学位移和³¹P－³¹P中的偶合常数的变化以及由ATP的存在所引起的¹¹³Cd的化学位移的变化.结果表明,在pH＞4.5的条件下,ATP主要以磷酸根和N₇同时对Cd²⁺配位;在pH值2.5～4.5的条件下,ATP主要以磷酸根和N₁同时对Cd²⁺配位,还存在少量的磷酸根和N₇同时配位的模式;而在酸性非常强的条件下(pH＜2.5),ATP不再与Cd²⁺相互作用。     

牛血清白蛋白与十二烷基硫酸钠作用的机理

利用电动势法得到了牛血清白蛋白(BSA)与十二烷基硫酸钠(SDS)相互作用的结合等温线. 通过四阶导数紫外光谱法和荧光光谱法研究了相互作用过程中芳香族氨基酸残基微环境极性的变化. 通过研究发现, 随着SDS浓度的逐渐增大, SDS在BSA上的平均结合数(v)逐渐增大, 色氨酸(Trp)残基所处微环境的极性在减弱后保持基本不变, 酪氨酸残基所处微环境的极性在明显增强后稍有减弱, 苯丙氨酸残基所处微环境的极性略有增强. 结果表明, 当v由0增大到14时, SDS主要结合在BSA的Trp-213附近并逐渐形成聚集体, 从而诱导BSA由结构域ⅡA 开始逐渐展开. 此后, SDS呈正协同作用的特点与BSA 结合, v急剧增大. 当v约为302 时, SDS在BSA上的结合基本达到饱和, BSA的构象趋于稳定.