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Ferrous-ion oxidation byThiobacillusferrooxidans was inhibited by 10-6 M Ag+ while a slight inhibition of growth was apparent with 10-7 M Ag+.
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| | Three different homogentisate oxidases have been isolated from the liver extracts of rate by starch electrophoresis. Similar results were obtained with relatively purified enzymes prepared according to a modification of the method described by Tokuyama.The electrophoretic mobility of homogentisate oxidase I surpasses that of serum albumin. The Michaelis constant of this enzyme has the value of 1.4×10~(-3)M for homogentisic acid. In the absence of ferrous-ion this enzyme preparation completely lo... | | 大白鼠肝脏尿黑酸氧化酶经丙酮,硫酸铵等步骤处理,再经过平板淀粉电泳的分离,此活力可以提高1000倍。利用平板淀粉电泳技术,由大白鼠肝脏中分离出三个具有尿黑酸氧化酶活力的酶蛋白。其中一个在电泳过程中移向正极,该部分酶制剂对反应系统中亚铁离子的要求比较严格,对尿黑酸的米氏常数等于1.4×10~(-3)M,高浓度底物有明显的抑制作用。第二个尿黑酸氧化酶亦趋向正极,但速度较慢,活力较低。第三个尿黑酸氧化酶的电泳位置接近负极端点,即使在没有任何辅因子参加的系统中亦具有一定水平的酶活力。后两个尿黑酸氧化酶对底物的米氏常数均为5.0×10~(-4)M,高浓度底物没有抑制现象发生。证明三个尿黑酸氧化酶催化同一个反应,而彼此的性质有区别,是一个具有多种分子形式的同工酶。本文对尿黑酸的自氧化以及影响自氧化的各种因子进行了分析讨论。 | | 文摘来源 | | Pure ferrous ion and benzene diazonium fluoroborate will not initiate the polymerization of acrylonitrile, while a small amount of copper ion is present, the polymerization of acrylonitrile will proceed smoothly and its rates of the polymerization will obey the following relationship :The mechanism of the redox initiation may be represented as follows:The polymerization of acrylonitrile can be initiated by p-nitrobenzene diazonium fluoroborate with the pure ferrous salt containing no... | | 以苯重氮硼氟酸盐与亚铁盐在微量铜离子存在时能引发丙烯腈聚合,聚合速率服从:R∝[φN_2~+]~(1/2)[Fe~(++)]~(1/4)[Cu~(++)]~(1/4),氧化还原引发历程为: Fe~(++)+Cu~(++) Fe~(+++)+Cu~+ φN_2~++Cu~+→φ·+N_2+Cu~(++) φ·+M→φM·→φMM·…该历程符合上述动力学关系。但使用对硝基苯重氮硼氟酸盐时,微量铜离子对聚合反应速率影响不大,与亚铁盐浓度在一定范围呈R∝[Fe~(++)]~(1/2)的关系,因此例的引发历程为: φN_2~++Fe~(++)→φ·+N_2+Fe~(+++) φ·+M→φM·→φMM·…苯环上推电子取代基降低了重氮基的氧化势,如对位取代甲氧基、甲基或没有取代基都不能用纯亚铁盐引发丙烯腈聚合,需有微量铜盐存在才能聚合。而拉电子取代基如对位取代硝基、羧基可用纯亚铁盐引发聚合。 | | 文摘来源 | | A new method of block eopolymerization by the use of aromatic tetraazonium salts redox initiators has been proposed. The precipitation polymerization of acrylonitrile in aqueous solution was initiated by the redox initiator of 4,4'-diphenyl tetraazonium fluoroborate and ferrous ion at low temperature (0℃). The polyacrylonitrile linked with diazonium groups and trapped free radicals on both ends by the precipitation polymerization was subjected to block-copolymerize with methacrylic acid or acryl... | | 提供了一种利用芳族双重氮盐进行嵌段共聚的新方法。研究了利用4,4′-联苯双重氮硼氟酸盐与亚铁盐引发丙烯腈低温沉淀聚合,使聚合物末端带上重氮基与包藏自由基,然后与甲基丙烯酸或丙烯酰胺进行嵌段共聚,所得嵌段共聚物为BAB型。研究了4,4′-联苯双重氮硼氟酸盐与亚铁盐引发丙烯酰胺水溶液聚合,使聚合物末端带有重氮基,再与丙烯腈或丙烯酸甲酯嵌段共聚。 | | 文摘来源 | |   | | << 更多相关文摘 |
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