167 resultados para Photosystem II reaction center


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LaCl3(15-crown-5), I was prepared by the reaction of LaCl(3)nH(2)O with 15-crown-5 and bipy (2,2'-bipyridyl). [LaCl2(phen)(H2O)(2)(mu-Cl)](2) .(15-crown-5). MeCN, II, was crystallized from a mixture of LaC1(3) . nH(2)O, phen (1,10-phenanthroline) and 15-crown-5 in MeOH/MeCN, Crystal structures of these two complexes have been determined by X-ray methods. The La(III) ion in I is coordinated by three Cl anions and five oxygen atoms of a crown ether. The two metal ions in II are bridged by two Cl anions and the crown ligand is hydrogen-bonded to the coordinated water molecules to form polymeric... crown/cation/cation/crown... chains.

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The binuclear complex [Ni(oxae)Ni(phen)2](ClO4)(2) . H2O (oxae=N,N'bis(2-aminoethyl) oxamido dianion, phen = 1, 10-phenanthroline) was prepared from the planar monomeric complex Ni(oxae) and characterized through analytical and spectroscopic measurements. The structure of [Ni(oxae)Ni(phen)(2)] (ClO4)2 . 3H(2)O was investigated by single-crystal X-ray analysis. The complex has an extended oxamido-bridged structure and consists of two nickel(II) ions, one of them in a square planar environment and another in a distorted octahedral environment. The Ni-Ni distance is 5.267 Angstrom.

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Three novel metal (II) phthalocyanine complexes were synthesized by cyclic tetramerisation reaction of a dicyano benzene component and different metal ions (Pd2+, Co2+, Zn2+). The structure of complexes was confirmed by elemental analysis, mass and IR spectrum. The excellent solubility of the complexes in benzene enabled us to obtain films by a spin-coating method. The films were characterized by IR, electronic spectral and AFM. The gas sensing properties to NO2 of the metal (II) phthalocyanine complex films were studied. In addition, the effects of different metal ions and the gas sensing temperature on the sensing properties were studied. (C) 2005 Elsevier B.V. All rights reserved.

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本论文在国内首次利用飞秒吸收光谱技术对PSII颗粒和PSII 核心复合物两个不同层次的PSII样品的原初反应过程进行了研 究。实验采用 400nm 激发, 520~700nm探测,时间分辨率为 120fs。通过多指数拟合和全局分析,对不同波长下的多条衰减 曲线同时采用一套时间组分进行解析,得到了不同波长下的各个 组分的衰减相关差异吸收谱(DADS)。 在 PSII 颗粒的研究中,通过对所有衰减曲线进行数据拟合,解析出了0.16ps、2.8ps、8.6ps、20.9ps、38.8ps和一个非衰减的组分。分析它们各自在520nm~700nm范围内的不同吸收变 化特点,我们得到以下结论: 1.在LHCII中,同一单体同一层中的Chlb与Chla分子之间 的能量传递时间常数约为0.16ps左右; 2.LHCII同一单体中,同一层中的Chla分子之间的能量传递时间常数约为 2.8ps 左右。这与在纯化的 LHCII研究中认为的一3ps组分为不同层的 Chlb→Chla的能量传递过程不同; 3.在PSII颗粒中,8.6ps 组分是与光化学过程有关的时间常数,它可能是从 LHCII 色素蛋白复合物向反应中心等的能量传递及在反应中心中的原初电荷分离过程的平均时间常数; 4.LHCII中不同单体之间的Chla之间的能量传递时间常数约为20.9ps。 在PSII核心复合物的研究中,通过对所有衰减曲线进行数据拟合,解析出了0.35ps、2.9ps、11.2ps、20.lps、36.5ps和一个非衰减的组分。分析它们各自在520nm~700nm范围内的不同吸收变化特点,并与PSII颗粒复合物所得结果相比较,我们得出以下结论: 1.PSII内周天线中相邻 Chla 之间的能量传递时间常数约为 0.35ps左右,这比LHCII中相邻Chlb与Chla之间的能量传递时间常数( 0.16ps )要长;这说明内、外周天线色素蛋白复合物 具有不同的色素空间排列。可以预见在PSII核心天线中相邻叶绿素分子之间的距离要比 LHCII中相邻叶绿素分子的8.3—10.5A 的距离要大一些。这在以前的研究中,并没有见到报导; 2.PSII内周天线中不相邻的Chla之间的能量传递时间常数 约为11.2ps; 3.在PSII核心复合物研究中,2.9ps 和 20.lps 两个组分均与光化学反应过程有关,推测原初电荷分离过程可能是有辅助叶绿 素分子参与的两步反应。

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Gonadotropin-releasing hormone (GnRH) is a conservative neurodecapeptide family, which plays a crucial role in regulating the gonad development and in controlling the final sexual maturation in vertebrate. Two differing cGnRH-II cDNAs of common carp, namely cGnRH-II cDNA1 and cDNA2, were firstly cloned from the brain by rapid amplification of cDNA end (RACE) and reverse transcription- polymerase chain reaction (RT-PCR). The length of cGnRH-II cDNA1 and cDNA2 was 622 and 578 base pairs (bp), respectively. The cGnRH-II precursors encoded by two cDNAs consisted of 86 amino acids, including a signal peptide, cGnRH-II decapeptide and a GnRH-associated peptide (GAP) linked by a Gly-Lys-Arg proteolytic site. The results of intron trapping and Southern blot showed that two differing cGnRH-II genes in common carp genome were further identified, and that two genes might exist as a single copy. The multi-gene coding of common carp cGnRH-II gene offered novel evidence for gene duplication hypothesis. Using semi-quantitative RT-PCR, expression and relative expression levels of cGnRH-II genes were detected in five dissected brain regions, pituitary and gonad of common carp. With the exception of no mRNA2 in ovary, two cGnRH-II genes could be expressed in all the detected tissues. However, expression levels showed an apparent difference in different brain regions, pituitary and gonad. According to the expression characterization of cGnRH-II genes in brain areas, it was presumed that cGnRH-II might mainly work as the neurotransmitter and neuromodulator and also operate in the regulation for the GnRH releasing. Then, the expression of cGnRH-II genes in pituitary and gonad suggested that cGnRH-II might act as the autocrine or paracrine regulator.

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Silica glass samples were implanted with 1.157 GeV Fe-56 and 1.755 GeV Xe-136 ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

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Silica and Merrifield resin were used as carriers for the support of alpha-diimine nickel(II) precatalysts for ethylene polymerization. The alpha-diimine ligands containing allyl were modified by introducing the reactive Si-Cl end-group, allowing their immobilization via a direct reaction of the Si-Cl groups with the silanols on silica surface or the hydroxyls on the ethanolamine-modified Merrifield resin. The resulting supported alpha-diimine ligands were characterized by analytical and spectroscopic techniques (NMR and Fr-IR).

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CE with tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) detection for the quantitative determination of isocyanates was first reported. Hexamethylene diisocyanate (HDI) and hexyl isocyanate (HI) were used as the model analytes. Commercially available N,N-diethyl-N'-methylethylenediamine was used as the derivatization reagent. It has both a secondary amine group and a tertiary amine group. The secondary amine group can quantitatively react with isocyanate group, and the tertiary amine group can react with Ru(bpy)(3)(2+) to produce strong ECL signal for sensitive detection. The derivatization reaction was almost instantaneous and is much faster than other reported derivative reactions using other derivative reagents.