Surface-Bound Selectin-Ligand Binding Is Regulated By Carrier Diffusion

Two-dimensional (2D) kinetics of receptor-ligand interactions governs cell adhesion in many biological processes. While the dissociation kinetics of receptor-ligand bond is extensively investigated, the association kinetics has much less been quantified. Recently receptor-ligand interactions between two surfaces were investigated using a thermal fluctuation assay upon biomembrane force probe technique (Chen et al. in Biophys J 94:694-701, 2008). The regulating factors on association kinetics, however, are not well characterized. Here we developed an alternative thermal fluctuation assay using optical trap technique, which enables to visualize consecutive binding-unbinding transition and to quantify the impact of microbead diffusion on receptor-ligand binding. Three selectin constructs (sLs, sPs, and PLE) and their ligand P-selectin glycoprotein ligand 1 were used to conduct the measurements. It was indicated that bond formation was reduced by enhancing the diffusivity of selectin-coupled carrier, suggesting that carrier diffusion is crucial to determine receptor-ligand binding. It was also found that 2D forward rate predicted upon first-order kinetics was in the order of sPs > sLs > PLE and bond formation was history-dependent. These results further the understandings in regulating association kinetics of surface-bound receptor-ligand interactions.

太行花MADS-box基因克隆、表达模式及功能分析

基因的重复（duplication）及其功能的多样性（diversification）为生物体新的形态进化提供了原材料。重复的基因通过表达方式和（或）编码序列的改变而导致其亚功能化（subfunctionalization）和（或）新功能化（neofunctionalization），从而使这些重复基因有可能保留在生物体中，增添生物的遗传稳定性（robustness）和多样性。MADS-box基因在植物（特别是在被子植物）的进化过程中发生了大量的基因重复事件而形成一个多基因家族。MADS-box基因家族的不同成员在植物生长发育过程中起着非常重要的作用，在调控开花时间、决定花分生组织和花器官特征，以及调控根、叶、胚珠及果实的发育中起着广泛的作用。开展对MADS-box基因家族成员的序列结构、表达模式及编码蛋白的功能研究可以为这些同源基因在生物体中的可能命运提供很好的实验依据。本研究以我国特有的蔷薇科物种太行花做实验材料，通过3’ RACE和5’ RACE方法从太行花中克隆了7个MADS-box家族的基因。序列和系统进化树分析表明这7个基因分别与拟南芥的MADS-box基因AG、SHP（SHP1/2）、PI、AP1、FUL和SEP1以及与矮牵牛MADS-box基因PhTM6具有很高的同源性并聚为一支，从而将这7个MADS-box基因分别命名为TrAG（Taihangia rupestris AG）、TrSHP（Taihangia rupestris SHP）、TrPI（Taihangia rupestris PI）、TrAP1（Taihangia rupestris AP1）、TrFUL（Taihangia rupestris FUL）、TrSEP1（Taihangia rupestris SEP1）和TrTM6（Taihangia rupestris PhTM6）。针对克隆的这些基因，具体进行了以下几方面的研究： 第一，对TrAG和TrSHP两个MADS-box基因进行了研究，它们分别属于AG亚家族中旁系同源进化系euAG和PLE进化系的成员。通过原位杂交的方法分析了旁系同源基因TrAG和TrSHP的表达方式是否发生了分化;构建组成型表达载体转化野生型拟南芥，分析了TrAG和TrSHP的编码蛋白的功能是否发生了改变;并进一步通过酵母双杂交的方法比较了TrAG和TrSHP的相互作用方式是否发生了分化。原位杂交分析表明，TrAG和TrSHP主要在雄蕊、心皮和胚珠中表达。在花发育过程中，TrAG起始表达比TrSHP早，在随后将形成雄蕊和心皮原基的分生组织区域以及雄蕊原基中表达;然而直到雄蕊原基出现前未检测到TrSHP的表达。在雄蕊原基形成之后，TrAG和TrSHP在发育的雄蕊、随后将产生心皮原基的分生组织区域以及心皮原基中表达。在花发育的晚期，TrAG在发育的柱头、花柱以及胚珠中均有表达，而TrSHP仅在胚珠中表达。35S::TrAG和35S::TrSHP转基因拟南芥植株表现出相似的表型，包括开花提前;莲座叶和茎生叶向腹卷曲、变小;花芽在时期13前即开放，萼片包裹不住花芽;萼片和花瓣分别被同源异型转化为心皮化和雄蕊化器官，并在萼片向腹面产生异位的胚珠;在茎生叶上产生柱头化的乳突和胚珠;子房弯曲;果实提前沿着开裂区裂开，暴露出胚珠。此外，也观察到35S::TrAG和35S::TrSHP转基因拟南芥植株的一些表型差异，35S::TrAG转基因拟南芥植株花芽呈暗绿色，而35S::TrSHP转基因拟南芥植株花芽呈黄绿色;不同与35S::TrAG转基因植株表型的是，35S::TrSHP转基因拟南芥植株花被脱落受到了抑制，偶尔可以观察到花丝基部融合，果实变短、育性降低。酵母双杂交分析表明TrAG可以与TrSEP3相互作用，而TrSHP不能与TrSEP3形成异源二聚体。以上研究结果表明做为旁系同源基因，TrAG和TrSHP在表达方式上发生了改变，在蛋白编码序列上保持了其祖先的功能，但是编码序列的一些差异还是导致它们之间生化作用方式的不同和一定程度上的亚功能化。基于以上研究结果并结合先前报道的在拟南芥、金鱼草和矮牵牛等物种中旁系同源基因的表达和功能数据，我们提出在不同物种中旁系同源基因在进化过程中维持部分功能冗余（redundant），但是也通过改变表达方式、编码蛋白的功能及蛋白相互作用方式呈现出不同形式的亚功能化和（或）新功能化。 第二，对TrPI基因的功能也进行了初步研究，它属于AP3/PI亚家族PI-like进化系的成员。原位杂交结果表明，TrPI主要在花瓣、雄蕊和胚珠中表达。显示出TrPI与拟南芥同源基因PI保守的表达模式。35S::TrPI转基因拟南芥植株莲座叶发生延迟、变小、并且第一至第三片莲座叶呈白色针状;莲座叶和茎生叶并不像野生型呈有规则的螺旋状排列;花序茎基部、中间或顶端发生2-3个分支;在茎生叶的叶腋内的花序抽出时间明显晚于野生型，并且很小甚至不能完全抽出而藏在叶腋内。低温条件下转基因植株莲座叶的表型更加明显，表现为莲座叶变为针状，无叶片，仅有叶柄结构。这明显不同于35S::PI转基因拟南芥植株的表型。此外，酵母双杂交分析表明TrPI自身可以形成同源二聚体。这种相互作用方式也不同与拟南芥中PI的相互作用方式。以上研究结果表明，TrPI可能与拟南芥PI具有保守的表达模式但编码的蛋白可能获得了新的功能。 第三，构建了一个AP1-like基因（TrAP1）的过量表达载体，转化野生型拟南芥植株，通过反向遗传学分析了TrAP1的功能。35S::TrAP1转基因拟南芥植株开花提前;花序以两朵花终止，形成terminal flower的表型;偶尔可以观察到雄蕊转化为花瓣化的器官;莲座叶呈黄绿色并且其边缘呈锯齿状。酵母双杂交分析表明TrAP1蛋白自身可以形成同源二聚体。这些结果表明TrAP1可能与拟南芥同源基因AP1具有保守的功能。

青岛市水资源复合系统动力学模拟研究

水资源是人类赖以生存和发展的最重要的物质资源之一，水资源的可持续利用是实现社会经济可持续发展的必要前提。随着人口的增加，社会经济的发展和人民生活水平的提高，青岛市水资源供需矛盾进一步凸显。本文在分析青岛市水资源利用现状的基础上，运行系统动力学方法，研究了青岛市水资源复合系统可持续利用状况，主要结论如下： （1）采用系统动力学Vensim-PLE软件，以水资源供需平衡为核心，建立了青岛市水资源-社会-经济-生态环境复合系统动力学模型，并以青岛市2000~2008年的统计资料作为基础数据检验了模型的有效性。为了提高模拟效果，分析了模型主要参数的敏感度，发现工业供水比例对模拟结果影响最大，生活供水比例、第三产业供水比例、回用水工业供水比例、污水处理投资系数及回用水生态环境供水比例等参数的敏感度依次减小。 （2）运用所建立的系统动力学模型模拟趋势条件下青岛市2009~2030年的水资源利用及需求状况。结果表明，现状趋势方案下青岛市2009~2030年的总需水量快速增加，2020年、2030年的总需水量分别为96190.6万吨、137300万吨；水资源供需差额急速增加，缺水程度越来越大，到2030年缺水程度达到0.5055；随着青岛市污水处理能力的提高，污水回用量增加，从3000万吨左右增加到接近10000万吨；现状趋势条件下2009~2030年青岛市GDP值快速增长，人口承载力逐渐上升，但上升趋势逐渐趋缓。 （3）假设了5种水资源发展方案：现状趋势发展型，提高污水处理投资系数，提高海水淡化产量，调整各行业用水定额，调整产业结构。用建立的系统动力学模型模拟分析了在这5种方案下的青岛市水资源可持续利用能力。综合比较这5种方案的优缺点，提出优化方案。优化方案1：将污水处理投资系数由0.001提高至0.003；从2009年起海水淡

Role of Bi3+ ions for Er3+ ions efficient 1.54 mu m light emission in Er/Bi codoped SiO2 thin film prepared by sol-gel method

Er/Bi codoped SiO2 thin films were prepared by sol-gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 degrees C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 mu m light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 gm reached maximum at 800 degrees C and decreased dramatically at 1000 degrees C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol-gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er-Bi-Si-O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED

Characterization of CdSe and CdSe/CdS core/shell nanoclusters synthesized in aqueous solution

CdSe nanoclusters overcoated with CdS shell were prepared with macapoacetic acid as stabilizer. The optical properties of CdSe nanoclusters and the influence of CdS shell on the electronic structures of CdSe cores were studied by optical absorption, photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Based on PL and PLE results and the theoretical calculation on fine structure of bandedge exciton, a model of formation of excimer within the small clusters was proposed to explain the large Stokes shift of luminescence from absorption edge observed in PL results. (C) 2000 Elsevier Science B.V. All rights reserved.

Correlated structural and optical investigation of terbium-doped zinc oxide nanocrystals

Tb3+-doped zinc oxide nanocrystals with a hexagonal wurzite structure were successfully prepared by reaction between Zn-O-Tb precursors and LiOH in ethanol. Good incorporation of Tb3+ in ZnO nanocrystals is proved by XRD, FTIR, PL and PLE measurements. The presence of acetate complexes to zinc atoms on particle surfaces is disclosed by FTIR results. Emission from both Tb3+ ions and surface states in ZnO matrix, as well as their correlation were observed. The luminescence mechanism is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.

Formation, structure and fluorescence of CdS clusters in a mesoporous zeolite

CdS clusters are formed in the pores of a mesoporous zeolite in which the size of the clusters may be adjusted. The size of the clusters increases as the CdS loading is increased. X-ray diffraction investigation shows that the lattice constants of the clusters contract upon increasing size. This contraction is attributed to an increase of the static pressure exercised by the zeolite framework as the clusters grow bigger. Both the excitonic and trapped emission bands are detected and become more intensive upon decreasing size. Three absorption bands appear in the photoluminescence excitation (PLE) spectra and they shift to the blue as cluster size decreases. Based on the effective-mass approximation, the three bands are assigned to the 1S-1S, 1S-1P and 1S-1D transitions, respectively. The size-dependence of the PLE spectra can also be explained. (C) 1997 Elsevier Science Ltd.

Characterization of CdSe and CdSe/CdS core/shell nanoclusters synthesized in aqueous solution

CdSe nanoclusters overcoated with CdS shell were prepared with macapoacetic acid as stabilizer. The optical properties of CdSe nanoclusters and the influence of CdS shell on the electronic structures of CdSe cores were studied by optical absorption, photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Based on PL and PLE results and the theoretical calculation on fine structure of bandedge exciton, a model of formation of excimer within the small clusters was proposed to explain the large Stokes shift of luminescence from absorption edge observed in PL results. (C) 2000 Elsevier Science B.V. All rights reserved.

VUV-UV photoluminescence spectra of strontium orthophosphate doped with rare earth ions

The measurements of VUV-UV photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra of rare earth ions activated strontium orthophosphate [Sr-3(PO4)(2):RE, RE = Ce, Sm, Eu, Tb] are performed. Whenever the samples are excited by VUV or UV light, the typical emission of Ce-3+,Ce- Sm3+, Eu3+, Eu2+ and Tb3+ ions can be observed in PL spectra, respectively. The charge transfer bands (CTBs) of Sm3+ and Eu3+ are found, respectively, peaking at 206 and 230nm. The absorption bands peaking in the region of 150-160 nm are assigned to the host lattice sensitization bands, i.e., the band-to-band transitions of PO43- grouping in Sr-3(PO4)(2). It is speculated that the first f-d transitions of Sm3+ (Eu3+), and the CTB of Tb3+ are, respectively, located around 165 (14 3) and 167 urn by means of VUV-UV PLE spectra and relational empirical formula, these f-d transitions or CT bands are included in the bands with the maxima at 150-160 nm, respectively. The valence change of europium from trivalent to divalent in strontium orthophosphate prepared in air is observe by VUV-UV PL and PLE spectra.

猪肝酯酶在不对称合成中的应用

猪肝酯酸PLE(Pig Liver Esterase)对双酯具有特殊的不对称水解性,而且可获得高产率和高光学纯的不对称水解产物。本文简要介绍PLE作为一种有效的酶催化剂,在温和的条件下,对双酯的不对称水解反应和在不对称合成中应用的近况。

微机控制的红热钢板动态测长仪

本文叙述了微机控制的红热钢板动态测长仪的原理、工程公式的导出、软件功能及其特点。