Ultrathin-film growth of para-sexiphenyl (II): Formation of large-size domain and continuous thin film

The large-size domain and continuous para-sexiphenyl (p-6P) ultrathin film was fabricated successfully on silicon dioxide (SiO2) substrate and investigated by atomic force microscopy and selected area electron diffraction. At the optimal substrate temperature of 180 degrees C, the first-layer film exhibits the mode of layer growth, and the domain size approaches 100 mu m(2). Its saturated island density (0.018 mu m(-2)) is much smaller than that of the second-layer film (0.088 mu m(-2)), which begins to show the Volmer-Weber growth mode.

Highly efficient electrochemiluminescence of functionalized tris(2,2 '-bipyridyl)ruthenium(II) enrichment of its co-reactants

An enhanced electrochemiluminescence (ECL) efficiency is obtained from the ruthenium complex tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) by introduction of an ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF(4)). Upon addition of 1% (v/v) BMImBF(4) to 0.1 mm Ru(bpy)(3)(2+) solution, a maximum increase in ECL intensity is obtained both at an indium tin oxide (ITO) electrode (15-fold) and at a glassy carbon (GC) electrode (5- to 64old). Furthermore, upon addition of 1% (v/v) BMImBF4 to 5 pm Ru(bpy)(3)(2+)/100 mm co-reactant systems at a GC electrode, IL adsorption occurs at the electrode surface, which results in a change of the polarity of the electrode surface. Such functionalization greatly improves the functions of both Ru(bpy)(3)(2+) and ionic liquids, as is demonstrated in the sensitive and selective concentration enrichment of the Ru(bpy)(3)(2+) co-reactants.

Catalysis of hydrotalcite-like compounds in liquid phase oxidation: (II) - Oxidation of p-cresol to p-hydroxybenzaldehyde

Hydrotalcite-like compounds (HTLcs): CoMAlCO3-HTLcs (M=Cu2+, Ni2+, Mn2+, Cr3+, Fe3+), were synthesized by coprecipitation and characterized with XRD and IR. The catalysis of these HTLcs and their calcined products were studied in the p-cresol oxidation, and the effects of the temperature of HTLcs calcination, the ratio of Co/Cu, different promoters, reaction temperatures and reaction times on reaction activities were investigated. It has been found that calcined HTLcs have higher activity than uncalcined samples and mechanical mixed oxides in this reaction. The best yield was obtained from the CoCuAlCO3-HTLc (Co/Cu/Al=3:1:1) calcined at 450 degrees C. A tentative reaction mechanism was also proposed. (C) 1998 Elsevier Science B.V.

Cloning and expression analysis in mature individuals of two chicken type-II GnRH (cGnRH-II) genes in common carp (Cyprinus carpio)

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.

Silver nanocluster-based fluorescent sensors for sensitive detection of Cu(II)

In this work, we report the first application of water-soluble fluorescent Ag nanoclusters in fluorescent sensors. The fluorescence of poly(methacrylic acid) (PMAA)-templated Ag nanoclusters was found to be quenched effectively by Cu2+, but not when other common metal ions were present. By virtue of the specific response toward the analyte, a new, simple, and sensitive fluorescent method for detecting Cu2+ has been developed based on Ag nanoclusters.

Synthesis and structure of new low dimensional polymeric haloplumbate(II) complexes [Pb4Br12(C40H40N8)] and [Pb4Cl12(C40H40N8)]center dot H2O

New low dimensional polymeric haloplumbate(II) complexes of the dication of (4,4'-bis(imidazolyl-ylmethyl)biphenyl) were synthesised and their crystal structures determined. Complex 1, [Pb4Br12(C40H40N8)], has cis-edge-shared, octahedral, lead bromide double chains. In compound 2 [Pb4Cl12(C40H40N8)]center dot H2O, the inorganic chains are corner-shared, square pyramidal chains of lead chloride. In both compounds the organic ammoniums form regular layers that alternate with the inorganic chains.

Effect of hydroxyl and amino groups on electrochemiluminescence activity of tertiary amines at low tris(2,2 '-bipyridyl)ruthenium(II) concentrations

ECL of several amines containing different numbers of hydroxyl and amino groups was investigated. N-butyldiethanolamine is found to be more effective than 2-(dibutylamino)ethanol at gold and platinum electrodes, and is the most effective coreactant reported until now. Surprisingly, ECL intensities of monoamines, such as 2-(dibutylamino)ethanol and N-butyldiethanolamine, are much stronger than that of diamines including N,N,N',N'-tetrakis-(2-hydroxyethyl)-ethylenediamine and N,N,N',N'-tetrakis-(2-hydroxypropyl)ethlenediamine. The striking contrast between ECL signals of the investigated monoamines and diamines may result from more significant side reactions of diamines, such as the intramolecular side reactions between oxidative amine cation radicals and reductive amine free radicals.

Extraction of zinc(II) and cadmium(II) by using mixtures of primary amine N1923 and organophosphorus acids

The extraction of zinc(II) and cadmium(II) from a chloride medium by mixtures of primary amine N1923 and organophosphorus acids [di-(2-ethylhexyl)-phosphoric acid, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH/EHP), isopropyl phosphonic acid 1-hexyl-4-ethyloctyl ester, bis(2,4,4-trimethylpentyl) phosphinic acid, bis(2,4,4-trimethylpentyl) monothiophosphinic acid, and bis(2,4,4-trimethylpentyl) dithiophosphinic acid] has been studied in the present paper. Results show that only the mixtures of N1923 + HEH/EHP and N1923 + Cyanex272 have synergistic effects on zinc(II), but the other mixtures have no evident synergistic effects. All six mixtures have no evident synergistic effects on cadmium(H). A possible explanation of the different extraction abilities is given based on the structure of the extractants. Furthermore, the possibilities of separating zinc(II) and cadmium(II) with these mixtures are investigated according to the extractabilities. It is possible to separate Zn2+ from bulk cadmium with N1923 and HEH/EHP mixtures and separate Cd2+ from bulk zinc with N1923 and Cyanex301 mixtures.

Synthesis, characterization, crystal structure and magnetic property of asymmetrical double Schiff base heterotrinuclear complex: Cu(II)-Co(II)-Cu(II)

An asymmetrical double Schiff-base Cu(II) mononuclear complex, HCuLp (H(3)Lp is N-3-carboxylsalicylidene-N'-5-chlorosalicylaldehyde-1,3-diaminopropane) and a heterometal trinuclear complex with double molecular structure (CuLp)(2)Co center dot 5H(2)O have been synthesized and characterized by means of elemental analyses, IR and electronic spectra. The crystal structure of the heterotrinucler complex was determined by X-ray analysis. Each asymmetric unit within the unit cell of the complex contains two heterotrinuclear neutral molecules (a) [CuLpCoCuLp], (b) [(CuLpH(2)O) CoCuLp] and four uncoordinated water molecules. In the two neutral molecules, the central Co2+ ions are located at the site of O-6 with a distorted octahedral geometry, one terminal Cu2+ ion (Cu(3)) at the square-pyramidal environment of N2O3, and the other three at the square planar coordination geometry with N2O2 donor atoms. Magnetic properties of the heterotrinucler complex have been determined in the temperature range 5-300 K, indicating that the interaction between the central Co2+ ion and the outer Co2+ ions is antiferromagnetic.

Computer simulation for effect of Pr(III) on Ca(II) speciation in human interstitial fluid

A multiphase model of metal ion speciation in human interstitial fluid was constructed and the effect of Pr(III) on Ca(II) speciation was studied. Results show that free Ca2+, [Ca(HCO3)], and [Ca(Lac)] are the main species of Ca(II). Because of the competition of Pr(III) for ligands with Ca(II), the percentages of free Ca2+, [Ca(Lac)], and [Ca(His)(Thr)H-3] increase gradually and the percentages of CaHPO4(aq) and [Ca(Cit)(His)H-2] decrease gradually with the increase in the total concentration of Pr(III). However, the percentages of [Ca(HCO3)] and CaCO3(aq) first increase and then begin to decrease when the total concentration of Pr(III) exceeds 6.070 x 10(-4) M.

A mechanistic model of algal photoinhibition induced by photodamage to Photosystem-II

Photoinhibition is a central problem for the understanding of plasticity in photosynthesis vs. irradiance response. It effectively reduces the photosynthetic rate. In this contribution, we present a mechanistic model of algal photoinhibition induced by photodamage to photosystem-II. Photosystem-IIs (PSIIs) are assumed to exist in three states: open, closed and inhibited. Photosynthesis is closely associated with the transitions between the three states. The present model is defined by four parameters: effective cross section of PSII, number of PSIIs, turnover time of electron transfer chains and the ratio of rate constant of damage to that of repair of D1 proteins in PSIIs. It gives a photosynthetic response curve of phytoplankton to irradiance (PI-curve). Without photoinhibition, the PI-curve is in hyperbola with the first three parameters. The PI-curve with photoinhibition can be simplified to the same form as the hyperbola by replacing either the number of PSIIs with the number of functional PSIIs or the turnover time of electron transfer chains with the average turnover time.

高等植物光系统II大量捕光色素蛋白复合体的稳定性研究

光合作用是地球上最重要的化学反应，它主要发生在叶绿体的类囊体膜上。光能是整个光合作用反应的驱动力，因此光能的捕获和传递过程将会直接影响整个生物体的光合作用表现。在高等植物中，光系统II（PSII）的大量捕光色素蛋白复合体（LHCIIb）作为最主要的、含量最多的光能捕获和传递器官，在光合作用过程中发挥着极其重要的作用。经过数十年的研究，认为LHCIIb主要的功能有以下四个方面：捕获和传递光能、光保护和过剩能量耗散、调节光能在两个光系统中分配和维持类囊体膜的结构。同时对其空间结构也在2.72Å的水平上进行了解析，发现每个单体含有14个叶绿素分子（Chl），其中8个叶绿素 a（Chl a）和6个叶绿素 b（Chl b），2个黄体素（Lut），一个新黄质（Neo）和一个紫黄质（Vio），3个跨膜α-螺旋和2个双亲α-螺旋。尽管目前对其空间结构和基本功能有了初步的了解，但以往研究均是对LHCIIb的三个色素蛋白复合体（Lhcb1、Lhcb2和Lhcb3）的混合研究，而关于Lhcb1、Lhcb2和Lhcb3各自的氨基酸组成、色素组成、各种光谱性质和稳定性研究还处于起步阶段。对Lhcb1、Lhcb2和Lhcb3各自的特性研究可以使我们更加深刻地理解LHCIIb的结构和功能。 本论文首先利用RT-PCR技术从豌豆（Pisum sativum L.）中提取了编码大量捕光色素蛋白复合体的三个脱辅基蛋白基因，分析了它们编码蛋白的氨基酸序列，并系统地研究了三个蛋白与其他物种中的三个蛋白之间的亲缘关系;然后在体外进行了成功的表达和与色素重组，进而对重组LHCIIb的色素组成及光谱特征进行了系统地对比和研究。实验结果表明，Lhcb1和Lhcb3的保守性高于Lhcb2，且Lhcb3最高，Lhcb1和Lhcb2的蛋白序列相似程度高于Lhcb3;Lhcb1同质三聚体的Neo含量和α-螺旋含量高于Lhcb1单体，Lhcb2单体和Lhcb3单体的α-螺旋含量高于Lhcb1单体;与Lhcb1单体和Lhcb2单体相比，Lhcb1同质三聚体和Lhcb3单体的荧光发射光谱明显红移，与核心复合物的光谱特征更加接近，这一区别可能更加有利于能量向核心传递;吸收光谱中表明，Lhcb1和Lhcb2存在两个Chl a吸收峰，根据分析超快吸收得到的模型（Amerongen & Grondelle，2001），这两个吸收峰可能代表Chl a的两个吸收中心。 在对LHCIIb各种基本特性研究的基础之上，本论文使用三氟乙酸（TFA）、离液剂尿素、离子性去污剂SDS、非离子型去污剂Triton X-100对Lhcb1单体进行了处理，使用不同温度对Lhcb1单体和同质三聚体、Lhcb2单体和Lhcb3单体进行处理。研究了它们在不同条件下的稳定性，主要结果如下： 1) 低浓度的尿素不能使Lhcb1变性，但可以影响色素之间的能量传递效率和相互作用。尽管SDS可以使Lhcb1解体，但解体后的蛋白仍旧保留了部分α-螺旋结构。TFA和非离子型去污剂Triton X-100可以使Lhcb1完全解体，并且可以完全破坏蛋白α-螺旋结构，TFA主要是通过影响色素结构和增加蛋白内部的分子间排斥力来破坏Lhcb1，而Triton X-100主要是通过破坏疏水作用力来破坏Lhcb1。高温可以使LHCIIb解体，但不能使蛋白二级结构完全消失。 2) 尿素、温度和Triton X-100均不引起色素本身的破坏，SDS和三氟乙酸使氢置换叶绿素卟啉环所螯合的镁离子，产生去镁叶绿素，造成色素本身结构的严重破坏。 3) 随着温度的升高，色素蛋白复合体的结构和功能会遭到破坏。在Lhcb1和Lhcb2中首先被破坏的是长波长吸收的Chl a。 4) .就功能而言，Lhcb1同质三聚体最为稳定，其次为：Lhcb1单体 > Lhcb3单体 > Lhcb2单体;.就结构而言，Lhcb1单体和Lhcb1同质三聚体相似，稍微较Lhcb2和Lhcb3稳定。 5) 不同处理方式均发现色素蛋白复合体的变性过程依次为：以Chl a为主的相互作用消失，其后依次为以Chl b为主的相互作用消失，以类胡萝卜素为主的相互作用，最后消失的是蛋白的二级结构。在结构受到破坏的同时，能量传递最先受到影响。 6) 解体过程并不是折叠过程的逆过程。