活性中心

This happens in a so called reaction center inPhotosystemⅡ, where a tetrameric chlorophylls (P680) absorb the solar light andinitiate photoinduced electron transfer reaction to the acceptors, quinone A and B. Thephoto-oxidized P680 retrieves the electron from a Mn4Ca cluster via a tyrosine, thelatter components are also called oxygen evolving center. After 4 photo-processes, twomolecular water are oxidized to a molecular oxygen.

在光系统二的活性中心，叶绿素P_(680吸收太阳光，将电子传递给电子受体、醌A和醌B，同时光氧化的P_(680)~+从释氧中心中得回电子(通过Tyr_z氧化Mn4Ca簇)，经过四次光诱导电子转移，两分子水最终被氧化生成一分子氧气。

Compared with the catalytic behaviors of the reference catalysts, CpTiCl〓 and n-CpTiCl〓, we could identify that the pendant ethereal group played an important role in this selective trimerization process.

将它们的催化性能与CpTiCl〓、n-CpTiCl〓比较，可以确定，氧对钛活性中心的配位对乙烯三聚反应起重要作用。

By comparing the catalytic behavior of S3/MAO and S8/MAO, a conclusion could be drawn that the coordination of the sulfur atom to the titanium center of the active species was essential for ethylene trimerization.

通过比较S3与S8不同的催化性能，可以认为，硫原子对钛活性中心可能存在配位，而这一配位对乙烯三聚反应起重要作用。

With two tripodal ligands, dtma and tmpa, dtma=diethylenetriamine-N'-acetate and tmpa=tris(2-pyridyl-methylamine and a polyamine ligand, trien (=triethylenetetramine), serving as terminal ligands, we synthesized 19 species of new imidazolate -bridged Cu-Zn, Zn-Zn and Cu-Cu, and other relating compounds, in which 〓 and 〓 complexes are model compounds of Cu, Zn-SOD.

用不等臂三脚架dtma(diethylenetriamine-N'-acetate)、直链trien和等臂三脚架tmpatris(2-pyridyl-methyl-amine为配体，合成了一系列咪唑桥联Cu-Zn、Zn-Zn和Cu-Cu等有关19个新化合物，其中两个异双核〓Cu〓和〓〓配合物为Cu，Zn-SOD活性中心的模型化合物。2。

HTERT is expressed in cancer cell lines despite promoter DNA methylation by preservation of unmethylated DNA and active chromatin around the transcription start site.

人端粒酶逆转录酶是一种核糖核蛋白酶，由端粒RNA和端粒酶蛋白组成的一种特殊逆转录酶，在激活端粒酶的过程中起限速作用，能以自身RNA为模板合成端粒序列以稳定端粒长度使细胞获得永生，也是人类端粒酶的活性中心，其表达是端粒酶活化的必须前题［2～4］。

Furthermore, we obtained a crystal structure of 17, which displays the relative position of Tyrto the high valent metal center and provided more useful information on mimicking the activecenter of OEC.

同时，我们得到化合物17的晶体结构，确定了化合物中各个基团的结构和相对位置，为更好的模拟释氧活性中心提供了很好的依据。

By a series of the characterization on its textural properties and reactivity, we have found that the zeolitic shell in the catalyst could effectively prevent the soluble palladium species from being leached into the reaction solution because of the special molecular sieving effect of the zeolitic shell, endowing the catalyst with high reusability.

然而，对很多的贵金属参与的工业反应而言，由于反应物原料本身含有痕量的含硫或含氮的化合物，在反应过程中，这些杂环化合物分子与贵金属的强相互作用导致了贵金属活性中心被覆盖而失活，造成催化剂的中毒。

The characterization of the coked catalyst shows that the deactivation of catalysts is caused by a jam of bulkier molecules, which are the alkylbenzenes from both reactants and products, so the deactivation cannot be avoided.

苯与长链烯烃的烷基化反应过程中，β沸石催化剂的失活是由于产品直链烷基苯本身和原料中带入的杂质芳烃逐渐堵塞孔道、阻止了反应物分子接近活性中心引起的，是由晶内开始逐渐向外发展的。

The catalyst combined with MAO or Al(i-Bu_3, AlEt_3 to form copolymerization active species, which was responsible for copolymerizing the ethylene andα-olefins to prepare branched polyethylene.

二酮锆/MAO Al(i-Bu_3、AlEt_3可以形成乙烯与α-烯烃的共聚活性中心，催化乙烯与特定链长的α-烯烃共聚得到了支化聚乙烯。

Fe2O3 acts as an activator more than a catalyst in the desulfurization reaction with lime. Fe2O3 acts as the "activation center" around which CaO particles are sulfurized. The new dispersal formation mode of product differs from the compact layer that used to be. And the pore structure of product layer on the surface of lime particles is optimized, which makes SO2 penetrate into core parts of lime more easily. As a result, the desulfurization reaction is developed deeper into the core parts of absorbent.

氧化铁所起的是改变石灰颗粒表层产物生成方式的活化作用，使反应生成物不会形成一个致密的外壳，而以氧化铁为活性中心进行硫化反应，形成了分散的硫酸钙产物堆积，改善了硫化过程中的表面孔隙结构，减少了石灰颗粒表面硫化产物层对反应气体向石灰颗粒内部扩散的阻力。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。