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981.
This paper illustrates the various aspects of the reactivity of the Cu(II)–Cu(I) system in biological systems, with one example of an enzymatic reaction in which Cu(II) alone is oxidizing enough to carry out the reaction (superoxide dismutase), one example in which a Cu(II)-bound peroxo intermediate is the active species (tyrosinase) and the examples of galactose oxidase and copper amine oxidases in which Cu(II) is associated with a redox active organic cofactor. In some cases, we will show some illustrations of biomimetic approaches developed in our laboratories, aimed at a better understanding of reaction mechanisms and at an original design of new catalysts with potential applications in synthetic chemistry. Some comments are given concerning the respective features of copper and iron. 相似文献
982.
Cr. Simionescu S. Dumitriu M. Popa M. Dumitriu D. Hritcu 《Colloid and polymer science》1984,262(9):705-711
In the present paper the immobilization of invertase and amyloglucosidase on Biozan R with dicyclohexylcarbodiimide as a catalyst is studied. The influence of some factors on the coupling reaction (duration, enzyme/support and catalyst/support ratios) as well on the acitvity of the coupled enzyme in followed. For both systems under study the value of the Michaelis-Menten constant is higher for the coupled enzyme than for the free one. 相似文献
983.
Gabriella Tamasi Claudia Bonechi Claudio Rossi Renzo Cini Agnese Magnani 《Journal of Coordination Chemistry》2016,69(3):404-424
A series of mononuclear binary and ternary Cu(I) complexes with formato, formamide, methylphenol, and methanethiolato ligands were optimized at DFT-B3LYP/6-31G** (BS1) and DFT-B3LYP/6-311++G** (BS2) levels of theory. The solvent effect was taken into account via PCM method (BS1W and BS2W, respectively). The coordination arrangement for [CuI(SCH3/S(H)CH3)(OOCH)]?/0 and [CuI(SCH3/S(H)CH3)(O(H)(C6H4)CH3)]0/+ was pseudo-linear and for [CuI(SCH3/S(H)CH3)(OOCH)(OC(H)NH2)]?/0 was pseudo-trigonal. The [CuI(S-S(H)CH3/CuI(S-SCH3)]+/0 link even to amide carbonyl and to general O(H)R residues (R=C6H5CH3). [CuI(SCH3)2(O(H)(C6H4)CH3)]? went towards dissociation of the O(H)(C6H4)CH3 ligand, whereas [CuI(S(H)CH3)2(O(H)(C6H4)CH3)]+ converged nicely, maintaining the hydroxy function linked to the metal. The trends of total electronic energies seemed to be significant, suggesting that linear CuIS2 coordination is more suitable than CuIS, CuIS3 and CuIS4 arrangements. The formation energies of [CuI(S(H)CH3/SCH3)(OOCH)]0/?1 were higher than those of [CuI(S(H)CH3/SCH3)2]+/? on starting from [CuI(S(H)CH3/CuI(SCH3)]+/0 by ca. 11–9 kcal mol?1 (BS2W). The structural arrangements, bond distances, and angles as well as computed spectroscopic parameters resulted in good agreement with experimental data for corresponding synthetic complexes and with metal site regions of several copper(I)-proteins. These data help in interpreting structural data of complex biological systems and in constructing reliable force fields for molecular mechanics computations. 相似文献
984.
Sébastien Giraudier Julien Picard Véronique Larreta Garde 《Macromolecular Symposia》2007,256(1):158-166
Summary: In various biological processes, a solid gel phase is produced which later dissolves. Similar ephemeral protein gels were obtained in vitro using two antagonistic enzymes, one generating and the other cleaving covalent bonds. Alternate sol/gel and gel/sol transitions should occur within such a system, generating transient gel phases. An experimental system consisting of gelatin, transglutaminase and thermolysin was first tested. The various gels obtained were programmed to dissolve after a determined time, without any change in temperature or medium composition, and constitute a completely new type of material which we term “Enzgels”. Varying temperature, but also the protein nature and concentration, the protease specificity, the ratio of the two antagonistic enzymes and, the activity of each enzyme, we were able to generate a full range of ephemeral gels with controlled life times and mechanistic properties. 相似文献
985.
固定化木瓜蛋白酶的制备和性质研究 总被引:10,自引:0,他引:10
多孔硅球固定化木瓜蛋白酶具有热增活性 .本文在前文研究的基础上 ,用载体交联法制备了甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶 .考察了固定化pH值、戊二醛浓度和给酶量对固定化木瓜蛋白酶活力的影响 .研究了固定化木瓜蛋白酶的性质 ,特别是热稳定性和耐热性 ,并与溶液酶和多孔硅球固定化木瓜蛋白酶进行了比较 .所制得的甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶的最适反应温度均达到了 80℃ ;90℃温育 1h后固定化酶的活力保持在 95 %以上 ;70℃温育处理 5h和 6h后固定化酶的活力也仍能保持在 90 %以上 .固定化木瓜蛋白酶的热稳定性和耐热性得到了显著提高 相似文献
986.
987.
Satoko Sugihara Kazunobu Toshima Shuichi Matsumura 《Macromolecular rapid communications》2006,27(3):203-207
Summary: High‐molecular‐weight poly(butylene succinate) (PBS) is prepared by the lipase‐catalyzed polymerization of dimethyl succinate and butane‐1,4‐diol via the formation of cyclic oligomers as a new strategy for the green production of bio‐based plastics. The cyclic oligomer is first produced by the lipase‐catalyzed condensation of dimethyl succinate and butane‐1,4‐diol in a dilute toluene solution using lipase from Candida antarctica, followed by the ring‐opening polymerization of the cyclic oligomer in a more concentrated solution or in bulk with the same lipase to produce PBS with an of 130 000. On the other hand, PBS is produced with an of 45 000 by direct polycondensation.
988.
一种含有氯乙氧功能基团的环状磷酸酯的酶促开环聚合 总被引:3,自引:2,他引:1
作为生物体内广泛存在的一类高分子——聚磷酸酯以其良好的生物相容性、生物可降解性及低毒性,一直受到人们的广泛关注.尤其是一些含有功能基团的聚磷酸酯,在基因转染、药物控制释放和组织工程等领域具有很好的应用前景.聚磷酸酯可通过金属催化剂开环聚合制备而成,但残留的微量金属催化剂可能会给材料带来潜在毒性. 相似文献
989.
M. Mohan Rao M. Jayalakshmi O. Schäf H. Wulff U. Guth F. Scholz 《Journal of Solid State Electrochemistry》2001,5(1):50-56
Lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4) were synthesized by self-propagating high-temperature combustion and their phase purity and composition were characterized
by X-ray diffraction and inductively coupled plasma spectroscopy. These transition metal oxides were mechanically immobilized
on the surface of paraffin-impregnated graphite electrodes and their cyclic voltammetric behaviour in aqueous alkali electrolytes
was examined. It was shown that both the oxides undergo proton insertion upon the reduction of Co3+ to Co2+ in LiCoO2 and Mn4+ to Mn3+ in LiMn2O4, while they deintercalate protons on the reverse oxidation. Scanning electron microscopy reveals spherical LiCoO2 particles with a very narrow size distribution. Energy dispersive X-ray detection proved the absence of metal cation intercalation.
Received: 30 August 1999 / Accepted: 11 November 1999 相似文献
990.
固定化谷氨酸脱羧酶性能的研究 总被引:4,自引:0,他引:4
本文首镒用羧甲基化的以N,N’-甲叉双丙烯酰胺交联的烯丙基葡聚糖凝胶生化树脂为新型载体,将谷氨酸脱羧酶固定在CM-CADB树脂上。研究了固定化GDC的活性与低物浓度,pH,温度的依存性;动态响应特性;热稳定性和寿命;求算了米氏常数和反应活化能;将固定化GDC酶柱与进样系统-离子活度分析器-计算机数据采集系统匹配,构成酶传感器谷氨酸检测装置,测定了固定化GDC酶柱的能斯特线性响应曲线,线性方程为y/ 相似文献