Engineering white light-emitting Eu-doped ZnO urchins by biopolymer-assisted hydrothermal method

With the presence of biopolymer-sodium alginate as additive, Eu-doped ZnO (zinc oxide) urchins consisting of nanorods were synthesized through a hydrothermal route. X-ray diffraction pattern makes evident the absence of phase other than wurtzite ZnO. Upon excited by 325 nm xenon laser, such nanostructured Eu-doped ZnO urchins emit white light, which originates from the luminescence of ZnO and the intra-4f transitions of Eu3+ ions. Besides acting as stabilizing agent, sodium alginate may also sensitize the Eu3+ ions in the nanostructures and facilitate the energy transfer from the host to Eu3+ ions. (c) 2006 American Institute of Physics.

ZnO-based hollow microspheres: Biopolymer-assisted assemblies from ZnO nanorods

Many efforts have been made in fabricating three-dimensional (3D) ordered zinc oxide (ZnO) nanostructures due to their growing applications in separations, sensors, catalysis, bioscience, and photonics. Here, we developed a new synthetic route to 3D ZnO-based hollow microspheres by a facile solution-based method through a water-soluble biopolymer (sodium alginate) assisted assembly from ZnO nanorods. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. Raman and photoluminescence spectra of the ZnO-based hollow microspheres were obtained at room temperature to investigate their optical properties. The hollow microspheres exhibit exciting emission features with a wide band covering nearly all the visible region. The calculated CIE (Commission Internationale d'Eclairage) coordinates are 0.24 and 0.31, which fall at the edge of the white region (the 1931 CIE diagram). A possible growth mechanism of the 3D ZnO superstructures based on typical biopolymer-crystal interactions in aqueous solution is tentatively proposed, which might be really interesting because of the participation of the biopolymer.

Shock tube study of JP-10 ignition delay time

JP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen.

冬枣果实对不同贮藏条件的生理反应及耐贮性研究

本文以我国特有的冬枣果实为试材，系统地研究了冬枣果实在室温、低温和不同O2和CO2浓度气调贮藏条件下的生理特性、风味品质和贮藏性，提出了适合于冬枣果实生理特性的气调指标和贮藏时间;分析了冬枣在不同贮藏条件下果实硬度、颜色、叶绿素和花青素、可溶性固形物、可滴定酸、Vc、乙醇和乙酸乙酯等物质成分的含量变化及与果实风味品质的关系;同时也分析了多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）、过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、多聚半乳糖醛酸酶（PG）和脂氧合酶（LOX）的活性变化情况以及丙二醛（MDA）含量和膜透性的变化情况，揭示了它们与冬枣果实转红、酒化、褐变、软化、衰老、及耐贮性的关系。对冬枣果实在气调贮藏中的生理反应和品质变化的研究，为形成冬枣果实采后商业化贮藏的系列配套技术提供了理论依据。试验结果表明： 1、冬枣果实在不同贮藏环境下品质的变化：随着贮藏时间的延长，冬枣果实Vc含量呈明显下降的趋势，CA处理能有效地抑制果实Vc含量的下降;不同贮藏条件对冬枣果实SSC影响不大;冬枣果实花青素的含量随贮藏时间逐渐下降，高O2浓度（70%）动态气调与其它处理相比，能更有效保持冬枣果实果皮的颜色及花青素和叶绿素的含量，以及果实的亮度、颜色饱和度和色度;同时，还能降低贮藏前期冬枣果实乙醇释放量。 2、冬枣果实在不同贮藏环境下生理的变化：（1） PG 酶是影响冬枣果实软化的主要因素，冬枣果实中存在内切和外切两种PG 酶，在冬枣果实的成熟过程中，Exo-PG和Endo-PG迅速积累，并呈现较高的活性，多聚半乳糖醛酸酶活性与冬枣果实的软化密切相关。CA贮藏与普通冷藏相比，可有效地抑制冬枣果实多聚半乳糖醛酸酶的活性和延缓果实软化，其中以5% O2的CA贮藏的效果最好。（2）膜质过氧化是造成冬枣果实褐变的主要因素，在室温下冬枣果实细胞膜透性随贮藏时间逐渐上升，CA贮藏在贮藏前中期可有效控制MDA含量的上升和果实褐变的发生，有利于降低膜脂过氧化程度，保护细胞膜结构并延缓果实衰老。冬枣果实褐变与PPO活性关系不大，但与膜透性及膜质过氧化作用的产物—丙二醛（MAD）含量变化显著相关。（3）冬枣果实采收时的SOD活性很低，在25 C下，果实SOD活性急剧上升，低温贮藏条件下，果实SOD活性出现两次高峰，第一次高峰为果实后熟的标志，第二次高峰标志着果实的衰老。（4）在不同贮藏条件下，冬枣果实PAL活性均随贮藏期的延长而呈现下降趋势。 3、影响冬枣果实贮藏性的生理因素：冬枣果实的衰老与活性氧代谢失调和防御体系活力下降有关，随着果实衰老的出现，果实的POD、CAT等保护酶活性均呈现明显下降的趋势。气调贮藏在前期能显著提高冬枣果实POD的活性，而在后期又显著抑制了POD活性的上升，说明POD在果实贮藏初期表现为保护效应，而在后期则表现为伤害效应。 4、冬枣果实适宜的贮藏条件：与普通冷藏相比，气调贮藏（CA）能明显地延缓果实衰老，减少腐烂和褐变，保持风味品质和延长贮藏时间。其中以较高O2浓度的（10% O2 + 0% CO2）气调贮藏效果最好。气调贮藏与杀菌剂配合有利于延长冬枣的贮藏期，0.1%的施保克和0.1%戴挫霉处理能有效控制冬枣果实贮藏期间的腐烂，延长贮藏时间，施保克的防腐效果好于戴挫霉。 5、拮抗菌和病原菌处理对冬枣果实抗性相关酶的诱导：接种拮抗菌+病原菌或只接种病原菌能诱导冬枣果实蛋白含量的显著升高，说明拮抗菌和病原菌处理诱导了果实病原相关蛋白的积累。在常温条件下，拮抗菌和病原菌处理抑制了冬枣果实的CAT酶活性，诱导了SOD和POD活性的上升。同时果实的蛋白含量也显著升高。在低温条件下，CAT和SOD活性受抑制，POD、PPO和 PAL活性被诱导并显著高于正常果实。这说明拮抗菌处理的冬枣果实可能通过加强氧化酶活性的方式来达到抗病的效果。拮抗菌和病原菌处理后，该部分组织的氧化酶活性加强，它们可以分解毒素，促进伤口愈合，抑制病原菌水解酶活性，从而抵抗病害的扩展。PAL是催化莽草酸途径的关键酶，可合成酚、植保素和木质素，而这些物质均与植物抗性有关。

Interaction between human interleukin-16 and CD4 receptor of HIV-1

AIM: To study the interaction between human interleukin-16 (IL-16) and the receptor CD4 (T-lymphocyte differentiation antigen) of human immunodeficiency virus type 1 (HIV-1). METHODS: Two structurally con served regions (SCRs) of human IL-16 were built by the SYBYL/Biopolymer module using the corresponding transmembrane (TM) domain of human interleukin-1 (HIL-4) and HIL-2 as the templates. The coordinates for amino-terminal residue sequence, carboxyl-terminal residue sequences, and cytoplasm loops were generated using Biopolymer's LOOP SEARCH algorithm. RESULTS: HIL-16 first formed a homodimer, then contacted with CD4 dimer further forming a dimeric complex. Subsequently, the dimeric complex constructed the tetrameric complex by two disulfide bridges between the cysteines of HIL-16 (Cys31-Cys31). CONCLUSION: The interaction model is useful to propose the action mechanism of HIL-16 and is beneficial for rational designing of novel anti-HIV drugs.

Molecular modeling on human CCR5 receptors and complex with CD4 antigens and HIV-1 envelope glycoprotein gp120

AIM: To investigate the interaction between human CCR5 receptors (CCR5) and HIV-1 envelope glycoprotein gp120 (HIV-1 gp120) and HIV-1 receptor CD4 antigens (CD4). METHODS: The structurally con served regions (SCR) of human CCR5 was built by the SYBYL/Biopolymer module using the corresponding transmembrane (TM) domain of bacteriorhodopsin (bR) as the template. The coordinates for amino-ter minal residue sequence, and carboxyl-terminal residue sequence, extracellular and cytoplasmic loops were generated using LOOP SEARCH algorithm. Subsequently the structural model was merged into the complex with HIV-1 gp120 and CD4. RESULTS: Human CCR5 interacted with both an HIV-1 gp120 and CD4. The N-terminal residues (especially Met1 and Gln4) of human CCR5, contacted with CD4 residues, mainly 7Nith one span (56 - 59) of CD4 in electrostatic interaction and hydrogen-bonds. The binding sites of human CCR5 were buried in a hydrophobic center surrounded by a highly basic periphery. On the other hand, direct interatomic contacts were made between ? CCR5 residues and 6 gp120 amino-acid residues, which included van der Waals contacts, hydrophobic interaction, and hydrogen bonds. CONCLUSION: The interaction model should be helpful for rational design of novel anti-HIV drugs.

快生型大豆根瘤菌（Rhizobium fredii）与野大豆（Glycine soja）相互作用的研究

快生型大豆根瘤菌（Rhizobium fredii）能浸染野大豆（Glycine soja）和栽培大豆（Glycine max）根部并形成固氮的根瘤。本文研究了R.fredii对野大豆的识别和侵染。通过研究R.fredii与大豆植物凝集素（SBL）结合和根毛吸附，R. fredii的EPS缺失突变株结瘤能力分析。结瘤；能力下降的突变株表面多糖分析等。发现了R.fredii与野大豆识别和侵染过程的特殊性。研究表明，（1）发现R.fredii与B.Jiaponicum和宿主的识别有不同的方式， 这在世界上是首次证明同一豆科宿主对不同的共生根瘤菌有不同的识别机制。这对认识宿主牧民性控制，研究扩大结瘤固氮范围等有重要意义；（2）第一个进行了R.fredii的Exo~-突变型的分离和鉴定。发现R. fredii的EPS产量和组成的严重发迹并不影响识别和侵染。说明在其他一些根瘤菌中发现的EPS作为宿主防御机制的保护层的作用。在R.fredii-野大豆和栽培大豆的共生结瘤中并不着急丰富了对根瘤菌EPS功能的新认识。并提出EPS作为保护层的作用与宿主植物类型有关的假设；（3）首次获得了LPS发生变化的R. fredii突变株Exol。并研究了其结瘤能力下降的现象与侵染能力和表面多糖变化的关系。提出R. fredii SG2的LPS可能在野大豆根毛郑曲和根瘤菌侵染过程中起重要作用。

Electrochemiluminescence detection based on Ruthenium(II) tris(bipyridine) immobilised in sulfonic-functionalised titania nanoparticles by ion exchange strategy

A novel Ruthenium(II) tris(bipyridine)-based solid-state electrochemiluminescence (ECL) sensor was developed in this paper. The sensor was fabricated by immobilising tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) in sulfonic-functionalised porous titania (TiO2-SO3H) nanoparticles via an ion exchange strategy, followed by employing environment friendly and stable biopolymer chitosan (CHIT) to entrap Ru(bpy)(3)(2+)/TiO2-SO3H onto the ITO electrode.

Silica Materials Doped with Bifunctional Ionic Liquid Extractant for Yttrium Extraction

Two new silica-based organic-inorganic hybrid materials (B104SGs and O104SGs) doped with a binary mixture of imidazolium and phosphonium ionic liquids have been synthesized and used as sorbents in batch system for rare earths (RE) separation. Imidazolium ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate (C(4)mim(+)PF(6)(-)) or 1-octyl-3-methylimidazolium hexafluorophosphate (C(8)mim(+)PF(6)(-)) acted as porogens to prepare porous materials and additives to stabilize extractant within silica gel.

Electrochemistry of Microperoxidase-11 (MP-11) on Glassy Carbon Electrode Modified with Chitosan

In this paper, microperoxidase-11 (MP-11) was immobilized on glassy carbon electrode surface modified with chitosan by physical adsorption. The direct electrochemistry and the electrocatalytic behaviours to O-2 and the H2O2 of MP-11 on glassy carbon electrode modified with chitosan were characterized by cyclic voltammetry. The results indicate that MP-11 on modified electrode displays a quasi-reversible electrochemical process coupled with proton transfer in the phosphate buffer solutions(pH = 7.12). Direct electrochemical reaction of MP-11 on modified electrode has been realized. MP-11 on modified electrode can catalyze reduction for O-2 and H2O2. Both of the catalytic reductions are surface-controlled electrochemical process.

Yttrium bis(alkyl) and bis(amido) complexes bearing N,O multidentate ligands. Synthesis and catalytic activity towards ring-opening polymerization of L-lactide

Methoxy-modified beta-diimines HL1 and HL2 reacted with Y(CH2SiMe3)(3)(THF)(2) to afford the corresponding bis(alkyl)s [(LY)-Y-1(CH2SiMe3)(2)] (1) and [(LY)-Y-2(CH2SiMe3)(2)] (2), respectively. Amination of 1 with 2,6-diisopropyl aniline gave the bis(amido) counterpart [(LY)-Y-1{N(H)(2,6-iPr(2)-C6H3)}(2)] (3), selectively. Treatment of Y(CH2SiMe3)(3)(THF)(2) with methoxy-modified anilido imine HL3 yielded bis(alkyl) complex [(LY)-Y-3(CH2SiMe3)(2)(THF)] (4) that sequentially reacted with 2,6-diisopropyl aniline to give the bis(amido) analogue [(LY)-Y-3{N(H)(2,6-iPr(2)-C6H3)}(2)] (5). Complex 2 was "base-free" monomer, in which the tetradentate beta-diiminato ligand was meridional with the two alkyl species locating above and below it, generating tetragonal bipyramidal core about the metal center. Complex 3 was asymmetric monomer containing trigonal bipyramidal core with trans-arrangement of the amido ligands. In contrast, the two cis-located alkyl species in complex 4 were endo and exo towards the 0,N,N tridentate anilido-imido moiety. The bis(amido) complex 5 was confirmed to be structural analogue to 4 albeit without THF coordination. All these yttrium complexes are highly active initiators for the ring-opening polymerization Of L-LA at room temperature.

Enantioselective iodolactonization catalyzed by chiral quaternary ammonium salts derived from cinchonidine

Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent.

Reagent-controlled asymmetric iodolactonization using cinchona alkaloids as chiral sources

A novel method for reagent-controlled asymmetric iodolactonization of 5-aryl-4-pentenoic acids is reported. This work uses carboxylate ion pairs combined with cinchona alkaloids as chiral sources of carboxylate anion for the first time leading to a mixture of two regio-isomeric iodolactones with moderate enantioselectivity (exo- 18.5% ee, endo-35.0% ee) under mild reaction conditions.

Electrogenerated chemiluminescence sensors using Ru(bpy)(3)(2+) doped in silica nanoparticles

A novel electrogenerated chemiluminescence (ECL) sensor based on Ru(bpy)(3)(2+)-doped silica (RuDS) nanoparticles conjugated with a biopolymer chitosan membrane was developed. These uniform RuDS nanoparticles ( similar to 40 nm) were prepared by a water-in-oil microemulsion method and were characterized by electrochemical and transmission electron microscopy technology. The Ru( bpy)(3)(2+)-doped interior maintained its high ECL efficiency, while the exterior nanosilica prevented the luminophor from leaching out into the aqueous solution due to the electrostatic interaction. This is the first attempt to branch out the application of RuDS nanoparticles into the field of ECL, and since a large amout of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode, the Ru( bpy)(3)(2+) ECL signal could be enhanced greatly, which finally resulted in the increased sensitivity. This sensor shows a detection limit of 2.8 nM for tripropylamine, which is 3 orders of magnitude lower than that observed at a Nafion-based ECL sensor. Furthermore, the present ECL sensor displays outstanding long-term stability.