Detection of molecular interactions with modified ferrocene self-assembled monolayers.

Ferrocene-terminated self-assembled monolayers (Fc-SAMs) are one of the most studied molecular aggregates on metal electrodes. They are easy to fabricate and provide a stable and reproducible system to investigate the effect of the microenvironment on the electron transfer parameters. We propose a novel application for Fc-SAMs, the detection of molecular interactions, based on the modification of the SAM with target-specific receptors. Mixed SAMs were fabricated by coimmobilization on Au electrodes of thiolated alkane chains with three different head groups: hydroxy terminating head group, ferrocene head group, and a functional head group such as biotin. Upon binding, the intrinsic electric charge of the target (e.g., streptavidin) modifies the electrostatic potential at the plane of electron transfer, causing a shift in the formal potential E degrees '. The SAMs were characterized by AC voltammetry. The detection mechanism is confirmed by measurements of formal potential as a function of electrolyte pH.

Ecophysiological response of Nerita oryzarum (Recluz), a gastropod, to variations in temperature, pH and salinity

During ecophysiological investigations on an intertidal gastropod, Nerita oryzarum (Recluz), of Mumbai shore, various biochemical changes could be recorded. Glycogen and lipid contents of N. oryzarum were found to decrease, whereas, water content increased with decreasing salinity. The rate of oxygen consumption declined with the decrease in salinity and also in highly acidic (pH 2) as well as highly alkaline (pH 10) sea water. The observed variations in the rate of oxygen consumption and changes in biochemical composition in the animal with changes in salinity, pH and temperature are probably the process of physiological and biochemical adjustments to the fluctuating environmental conditions in the intertidal region.

蓝藻应答高 pH 胁迫的亚细胞蛋白质组学研究

蓝藻是迄今地球上发现的最古老、分布最广和最具多样性的光合自养原核生物，其细胞结构简单，具有类似于植物的光合作用，是研究光合作用及其它代谢过程重要的模式生物。由于这类生物起源于远古前寒武纪，但至今依然繁多，在极端寒冷的南北极冰湖和近于沸腾温度的温泉，以及高盐、强碱的极端环境中均有存在,它们在漫长的进化过程中如何应对灾难性环境、针对随时可能遭遇的不同胁迫环境因子形成了怎样的分子适应机制，是近年来倍受关注但仍未诠释的问题之一。由于蓝藻与高等植物叶绿体在进化上密切相关，搞清楚这类生物适应不同胁迫环境因子的分子基础及其作用机制，对从进化的角度理解光合生物与环境相互作用、通过同源性发现作物抗逆育种新靶标，有重要的理论和实践意义。 逆境应答蛋白的表达是细胞对逆境胁迫的主要适应机制之一。在特定的逆境条件下，细胞通常会表达一组蛋白质，用于识别与传递环境胁迫信号、稳定细胞内环境、消除并修复逆境造成的损伤等。因此，逆境应答蛋白的系统鉴定和功能确认，是揭示逆境条件下细胞代谢网络及抗逆性分子机制的关键。单细胞模式蓝藻基因组序列的确定，极大地推动了蓝藻细胞蛋白质组成模式研究，也为系统发掘蓝藻逆境应答蛋白、理解和揭示分子适应机制提供了新的切入点。Synechocystis 6803是第一个完成基因组测序的放氧光合模式生物。由于其具有易培养、可转化、对环境条件变化反应快等优点，以该藻种为材料所展开的逆境应答特别是盐胁迫蛋白质组研究方面已经取得了重要的进展，而对高pH胁迫的蛋白质组研究还鲜有报道。因此，本论文以Synechocystis 6803为材料，从分离纯化的亚细胞组分入手，采用蛋白质组学研究手段，对蓝藻细胞应答高pH胁迫的蛋白质代谢网络进行探讨。利用蔗糖密度离心和水溶性两相分离法相结合的方法，分别获得了对照（pH7.5）和处理（pH11）细胞的质膜、外膜和类囊体膜，并分别构建了包括可溶性蛋白和膜组分的一维和二维蛋白质凝胶电泳图谱。分析结果表明，高pH胁迫下质膜和可溶性蛋白蛋白组分的变化较外膜和类囊体膜蛋白组分更为明显。在考马斯亮兰染色胶上共发现有近110个蛋白点上调或下调表达，其中有82个蛋白点来源于质膜。对质膜蛋白进行的差异荧光标记双向电泳（2-D DIGE）分析结果与考马斯亮兰染色结果基本一致。对质膜上的82个蛋白点进行胶内消化和MALDI-TOF和MALDI-TOF/TOF质谱鉴定，得到了39个不同基因产物，其中25个是上调蛋白，14个是下调蛋白。在这些发生变化的蛋白中，近1/3是ABC型转运蛋白，如3个磷转运蛋白（Sll0679，Sll0683，Sll0684）均在高pH胁迫下明显上调。其它高pH响应蛋白包括参与光合作用（PsaF，Sll0819；CpcA，Sll1578）、呼吸作用（CoxB，Sll0813）以及细胞分裂过程的蛋白（MinD，Sll0289）。还有LexA repressor (Sll1626)和Guanylyl cyclase(Cya2，Sll0646)等起调控作用的蛋白质。此外发现8个高pH胁迫响应蛋白为功能未知的新蛋白。生物信息学预测结果显示，在已鉴定的质膜响应蛋白中有17个蛋白具有信号肽。6个蛋白为具有跨膜域的膜蛋白，其中的3个膜蛋白是首次被证明定位于质膜上，且其表达与高pH胁迫有关。这些研究结果对从分子水平理解蓝藻细胞主动应对高pH胁迫、维护细胞内pH相对稳定机制有重要启示。

Response of extract release volume to the variations in pH and microbial load during spoilage of fish at refrigeration temperature

This report briefly describes the microbial status and storage properties of fish raised under composite fish culture in sewage fed ponds.