连续一级反应的热动力学研究

本文把时间比法引入热动力学研究,建立了连续一级反应的热动力学研究法,并用来研究了一个连续反应体系的热动力学,验证了该方法的正确性.     

紫色酸性磷酸酯酶模型化合物水解ATP的研究

紫色酸性磷酸酯酶（PAPS）是含铁的糖蛋白，能够从植物和动物体内分离出来，在微酸性条件下，能催化水解磷酸酯阻］，该类酶具双核铁中心活性部位，每个蛋白有两个铁原子，两个铁原子以ellelll形式存在时，具有催化活性·近年来，人们对研究磷酸酯水解酶感兴趣，是因为这个课题     

Semiempirical Molecular Orbital Studies of the Acylation Step in the Lipase‐Catalyzed Ester Hydrolysis

In this study, we present the results from the semiempirical molecular orbital calculations for the acylation step in the lipase‐catalyzed ester hydrolysis. The results reveal that the lowest energy path for the formation of the tetrahedral intermediate is for the serine residue of the catalytic triad to attack the substrate, followed by coupling heavy atom movement and proton transfer. The calculations of four active site models show that the cooperation of the aspartate group and the oxyanion hole is capable of lowering the activation energy by about 16 kcalmol^?1. Our results further suggest that the lipase‐catalyzed ester hydrolysis adopts the single proton transfer mechanism.     

高分子药物研究Ⅰ．5－氨基水杨酸与二元羧酸缩聚物的合成

通过５－氨基水杨酸与二元羧酸进行缩聚反应，合成了六种主链含有５－氨基水杨酸的高分子化合物，用红外光谱和元素分析确定了聚合物的结构。聚合物水解实验表明，它们在酸性、中性和碱性介质中均能水解，水解速率（ｒ）的大小依次为ｒｐＨ＝１３．０＞ｒｐＨ＝７．０＞ｒｐＨ＝２．０。     

L1 β-Lactamase催化反应机理研究

用混合量子力学和分子力学(QM/MM)方法和密度泛函理论讨论了L1 β-Lactamase催化Nitrocefin水解的过程, 研究结果表明, 反应为多步反应: 第一步亲核进攻反应为反应的决速步骤, 并且伴随着酰胺键的断裂, 第二步反应为质子迁移反应. 同时讨论了金属锌在反应中的作用.     

Synthesis and Hydrogen-Bond Patterns of Aryl-Group Substituted Silanediols and -triols from Alkoxy- and Chlorosilanes

Organosilanols typically show a high condensation tendency and only exist as stable isolable molecules under very specific steric and electronic conditions at the silicon atom. In the present work, various novel representatives of this class of compounds were synthesized by hydrolysis of alkoxy- or chlorosilanes. Phenyl, 1-naphthyl, and 9-phenanthrenyl substituents at the silicon atom were applied to systematically study the influence of the aromatic substituents on the structure and reactivity of the compounds. Chemical shifts in ²⁹Si NMR spectroscopy in solution, correlated well with the expected electronic situation induced by the substitution pattern on the Si atom. ¹H NMR studies allowed the detection of strong intermolecular hydrogen bonds. Single-crystal X-ray structures of the alkoxides and the chlorosilanes are dominated by π-π interactions of the aromatic systems, which are substituted by strong hydrogen bonding interactions representing various structural motifs in the respective silanol structures.     

The influence of moisture on deprotonation mode of imidazolinium chlorides with palladacycle acetate dimer

Deprotonation of 1,3-diorganyl imidazolinium salts, 1, with N,C-type palladacyclic acetate dimer 2 afforded novel NHC coordinated complexes 3 along with ring opening hydrolysis products 4, which may coordinate to palladium center via NH group to give 5a. The hydrolysis necessitates the study of NHC complex formation in anhydrous media. The new compounds were characterized by spectroscopic methods and three of them (3c, 4c, 5a) by X-ray single-crystal diffraction studies.     

Hydrolysis of the amide bond in N-acetylated l-methionylglycine catalyzed by various platinum(II) complexes under physiologically relevant conditions

The hydrolytic reactions between various Pt(II) complexes of the type [Pt(L)Cl₂] and [Pt(L)(CBDCA-O,O′] (L is ethylenediamine, en; (±)-trans-1,2-diaminocyclohexane, dach; (±)-1,2-propylenediamine, 1,2-pn and CBDCA is the 1,1-cyclobutanedicarboxylic anion) and the N-acetylated l-methionylglycine dipeptide (MeCOMet-Gly) were studied by ¹H NMR spectroscopy. All reactions were realized at 37 °C with equimolar amounts of the Pt(II) complex and the dipeptide at pH 7.40 in 50 mM phosphate buffer in D₂O. Under these experimental conditions, a very slow cleavage of the Met-Gly amide bond was observed and this hydrolytic reaction proceeds through the intermediate [Pt(L)(H₂O)(MeCOMet-Gly-S)]⁺ complex. In general, it can be concluded that faster hydrolytic cleavage of the MeCOMet-Gly dipeptide was observed in the reaction with the chloride complex than with corresponding CBDCA Pt(II) complexes. The steric effects of the Pt(II) complex on the hydrolytic cleavage of the amide bond in the MeCOMet-Gly dipeptide were also investigated by ¹H NMR spectroscopy. It was found that the rate of hydrolysis decreases as the steric bulk of the CBDCA and chlorido Pt(II) complexes increase (en > 1,2-pn > dach). These results contribute to a better understanding of the toxic side effects of Pt(II) antitumor drugs and should be taken into consideration when designing new potential Pt(II) antitumor drugs with preferably low toxic side effects.     

The effect of the migrating group structure on enantioselectivity in lipase-catalyzed kinetic resolution of 1-phenylethanol

We have studied the effects of the acyl moiety on the enantioselectivity of three lipases: Candida antarctica B, Pseudomonas cepacia and Candida cylindracea, frequently used in kinetic resolutions by acylation or hydrolysis. The size of the acyl group was examined using various enol esters during the transesterification of 1-phenylethanol and the hydrolysis of the corresponding phenylethylesters. C. antarctica-B lipase showed the highest selectivity in the transesterification of 1-phenylethanol with isopropenyl and vinyl acetate, vinyl decanoate, vinyl laurate, (E > 200). The esters 1-phenyl -ethyl-acetate, decanoate and laurate are also hydrolyzed with high selectivities (E > 150) with CAL-B. The results can be correlated to the three-dimensional form of each lipase. The effect of the migrating group on the reactivity and selectivity of the lipases are discussed for both reactions.     

聚乳酸立构复合物的研究最新进展与应用展望

立构复合型聚乳酸(SC-PLA)由于聚左旋乳酸(PLLA)与聚右旋乳酸(PDLA)分子链之间强烈的相互作用,可以使熔点提高约50℃,改善了聚乳酸在耐热性上的不足,同时这种立构复合结构使聚乳酸的力学性能、结晶性能、耐水解性等也得到提升.立构复合型聚乳酸的合成新进展主要集中在嵌段型SC-PLA的制备,同时广泛采用X射线衍射...