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.     

聚酯工业缩聚过程的微观质量数学模型

介绍了一个工业化聚酯（ＰＥＴ）生产过程中的缩聚模型。模型从聚合反应机理出发,考虑了所有的主反应和主要的副反应,以实测的工艺操作参数为输入,以各反应釜,特别是终端产品的聚工,平均相对分子及相对分子质量分布参数为输出。文章讨论了预缩聚和终缩聚阶段中副产物－－小分子的脱出特点及挥发量的计算,最后介绍了建模方法和模型现场运行结果。     

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。     

鲤亚目几种名优鱼的随机扩增多态性DNA分析

采用OPA、OPC和OPM三组共60条随机引物对鲤亚目的七种名优鱼和一种杂交品种进行了随机扩增多态性DNA(m)分析,对其中35个引物的扩增条带进行了统计,计算了它们之间的遗传相似率和遗传距离,在此基础上,利用UPGMA聚类分析建立了它们之间的亲缘关系,结果与传统分类是一致的,并且将杂交品种与纯种区分开来,实验还初步筛选了7种鱼的RAPD分子标记,探讨了用R6PD技术来鉴定名优鱼应用的可行性。     

废水处理系统中功能菌株特异分子标记

用40条10碱基随机引物对油脂化工废水处理系统中分离到的降解脂肪酸和脂肪胺功能菌株FA-2。FA-3及对照菌株进行RAPD分析。筛选出长度为700bp的FA-2的特异性片段,并克隆到pMD 18-T载体上．根据测序结果,设计了1对SCAR(sequence characterized anlplfied region)引物,通过SCAR-PCR反应,获得SCAR标记,并通过对20个培养样品进行PCR扩增,验证了标记特异性．结果表明该标记可作为特异的分子标记用于污水处理系统中功能菌株FA-2的监测．     

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.     

Special IR properties of palladium nanoparticles and their aggregations in CO molecular probe infrared spectroscopy

Dispersed Pd nanoparticles (Pdn) have been synthesized by reducing H2PdCI4 with ethanol, and stabilized using poly(vinylpyrrolidone) (PVP). The Pdn is applied to the glassy carbon substrate to form a thin film, and then the potential cyclic scanning at 50 mV.s^-1 from -0.25 to 1.25 V was carried out for about 30 min to form the aggregations of Pdn (Pdn^ag). FTIR spectroscopy of both transmission and reflection modes was employed to study CO adsorption on Pdn and Pdn^ag in both solidlliquid and solidlgas interfaces. It has been revealed that CO adsorption on Pdn film yields two IRbands near 1964 and 1906 cm-1, which are assigned to IR absorption of CO bonded on asymmetric and symmetric bridge sites, respectively. In contrast to the IR properties of CO adsorbed on Pdn, only species of CO bonded on asymmetric bridge sites was determined on Pdn^ag, and the direction of the IR band near 1963 cm^-1 is completely inverted. The full width at half-maximum (FWHM) of the COB^as band near 1964 cm^-1 is measured to be 14 cm^-1 on Pdn film, while it is 24 cm^-1 on Pdn^ag film. The results of the present study demonstrated that the inverting of the IR band direction is a general phenomenon that is closely related to the interaction between nanoparticles in aggregation of Pdn.