T902抗泡剂结构分析及性能研究

由高分子反应统计理论,结合~1H-NMR及(13)C-NMR方法,分析了T902抗泡剂的序列结构,获得了该三元无规共聚物分子的链段分布函数。系统研究了分子结构对消泡性能的影响,指出了改善抗泡剂配伍性能的正确途径。     

脉冲色谱法测O2在炭分子筛上的吸附与扩散参数

建立了脉冲色谱法测炭分子筛填充柱中气体吸附和扩散参数实验装置。考察了不同载气流速下Ｏ２的脉冲应答曲线，并根据炭分子筛二离散孔结构模型计算出其一级绝对矩和二级中心矩。由一级绝对矩求得Ｏ２在炭分子筛上的吸附平衡常数值为４．９１．由二级中心矩求得Ｏ２在炭分子筛中的大孔扩散系数　Ｄｙ和微孔扩散参数　Ｄｘ／Ｒ２ｘ值分别为１．４６１×　１０－４ｃｍ２·ｓ－１和０．１９６ｓ－１．这种动态下测Ｏ２在炭分子筛上的吸附和扩散参数的方法简便而实用。     

核酸序列的模糊聚类与分子进化

将核酸序列(编码区)分成几类,求出每类的平均信息参数(D_L),用模糊聚类的方法研究它们的相似性和同源性,求出各级相似分岔值并导出动态聚类图.证明了短程相似分岔与序列进化有明显的相性,即L=2-5的一级相似分岔值与物种出现地质年代的对数保持较好的线性关系.     

Triplet repeat disorders: discussion of molecular mechanisms

Comparison of the growing number of disorders known to be associated with triplet repeat expansions reveals both common features and a diversity of molecular pathways. Despite significant progress towards the characterization of proteins coded by the mutant genes, the complex nature of these disorders requires identification of all molecular components of the triplet repeat pathways. In this brief review we will discuss recent progress in determining the molecular mechanisms of disorders with unstable trinucleotide mutations. Received 13 January 1999; received after revision 8 March 1999; accepted 9 March 1999     

Structure and electrical characteristics of Nb-doped SrTiO3 substrates

Strontium titanate (SrTiO3) has been widely used as substrates for growing perovskite oxides thin films be- cause SrTiO3 is chemically and compositionally stable, and has small lattice mismatch with many perovskite oxides[1―3]. It is known that SrTiO3 it…     

阳离子管式聚合反应过程的实验研究与数学描述（Ⅰ）模型与求解

从典型的阳离子管式聚合反应过程出发，以反应度法和生成函数为工具，建立了描述此类反应过程的反应动力学。热力学及产品分子量分布的数学模型．并介绍了求解此类以偏微分方程为特征的数学模型的方法。     

Strategies for the design of inhibitors of aldose reductase, an enzyme showing pronounced induced-fit adaptations

Aldose reductase is involved in the polyol pathway, catalyzing the reduction of glucose to sorbitol. However, due to pronounced binding site adaptations, the enzyme can operate on a broad palette of structurally diverse substrates ranging from small aliphatic and aromatic aldehydes up to steroid-type ligands. A comparative analysis of the presently accessible crystal structures of aldose reductase complexes reveals four binding-competent protein conformations. Additional relevant conformers are detected through molecular dynamics simulations. They indicate an equilibrium of several conformers which is shifted towards the binding-competent geometries upon ligand binding. Such a manifold system with several alternative binding site conformers requires some tailored concepts in virtual screening. We followed two strategies, both successfully suggesting new micromolar inhibitors. In a first attempt, we concentrated on one preferred conformer and performed a virtual screening, assuming that the binding pocket of aldose reductase adopts only this conformation. In a second approach, we followed a ligand superpositioning method. Ligands were extracted in their bound conformations from three different crystal structures, all accommodating the ligands with different active site conformations. After merging these ligands into one supermolecule, mutual alignments were computed, taking candidate ligands from a screening database. The latter strategy also retrieved several structurally new inhibitors of micromolar potency.     

Real time monitoring of nucleic acids ligation based on molecular beacon

The replication, ligation and repair of nucleic acids are essential life processes that based the survival, pro-creation and evolution of creatures. These interactions involving proteins (enzymes) and nucleic acids have fas-cinated great interest of scientists[1]. The nucleic acids ligation has been revealed that it is catalyzed by ligase and co-enzyme (ATP or NAD)[2—4]. Along with in-depth re-search, the nucleic acids ligation becomes a significant and common tool employed in bioengineerin…     

The plasma membrane proton-translocating ATPase

Living cells require membranes and membrane transporters for the maintenance of life. After decades of biochemical scrutiny, the structures and molecular mechanisms by which membrane transporters catalyze transmembrane solute movements are beginning to be understood. The plasma membrane proton-translocating adenosine triphosphatase (ATPase) is an archetype of the P-type ATPase family of membrane transporters, which are important in a wide variety of cellular processes. The H+-ATPase has been crystallized and its structure determined to a resolution of 8 angstrom in the membrane plane. When considered together with the large body of biochemical information that has been accumulated for this transporter, and for enzymes in general, this new structural information is providing tantalizing insights regarding the molecular mechanism of active ion transport catalyzed by this enzyme.