Direct electrochemistry of horseradish peroxidase immobilized in calcium carbonate microsphere doped with phospholipids

Protein electrochemistry affords a direct method to study the biological electron transfer processes. However, supplying a biocompatible environment to maintain the native state of protein is all-important and challengeable. Here, we chose vaterite, one of the crystalline polymorphs of calcium carbonate, with highly porous nature and large specific surface area, which was doped with phospholipids, as the matrix to immobilize horseradish peroxidase (HRP). The integrity of HRP was kept during the simple immobilization procedure. By virtue of this organic/inorganic complex matrix, the direct electrochemistry of HRP was realized, and the activity of HRP for catalyzing reduction of O-2 and H2O2 was preserved.

Self-assembled monolayer growth of phospholipids on hydrophobic surface toward mimetic biomembranes: Scanning probe microscopy study

Atomic force microscopy (AFM) and lateral force microscopy (LFM) were used simultaneously to analyze a model membrane bilayer structure consisting of a phospholipid outer monolayer deposited onto organosilane-derivatized mica surfaces, which were constructed by using painting and self-assembly methods. The phospholipid used as outer monolayer was dimyristoylphosphatidylcholine (DMPC). The hydrocarbon-covered substrate that formed the inner half bilayer was composed of a self-assembly monolayer (SAM) of octadecyltrichloroorganosilane (OTS) on mica. SAMs of DMPC were formed by exposing hydrophobic mica to a solution of DMPC in decane/isobutanol and subsequently immersing into pure water. AFM images of samples immersed in solution for varying exposure times showed that before forming a complete monolayer the molecules aggregated into dense islands (2.2-2.6 nm high) on the surface. The islands had a compact and rounded morphology. LFM, coupled with topographic data obtained with the atomic force mode, had made possible the distinction between DMPC and OTS. The rate constant of DMPC growth was calculated. This is the first systematic study of the SAM formation of DMPC by AFM and LFM imaging. It reveals more direct information about the film morphology than previous studies with conventional surface analytical techniques such as infrared spectroscopy, X-ray, or fluorescence microscopy.

内蒙古多伦草原土壤微生物多样性对全球变化的响应

气候变暖和氮沉降是全球变化现象中最为重要和广为关注的两个方面，它们给陆地生态系统带来了深刻的影响。目前，已有众多研究就二者对地上植被的影响展开了大量工作;而作为陆地生态系统的另一重要生命组分，土壤微生物群落对二者的响应与适应机制还不明了，还需要相关工作的不断补充和完善。本文正是在温带典型草原通过设置增温、施氮等模拟控制实验，探讨增温、施氮及其交互效应对草原生态系统土壤微生物群落多样性和功能多样性的影响，使我们对该地区土壤微生物群落的响应与适应有了一个初步的了解，有助于全面分析和评估气候变化对温带典型草原生态系统的影响。 目前，全球变暖表现出时间上的不均衡性，即夜间增温的幅度要大于白天增温的幅度，而且这种现象在欧亚大陆尤为普遍。这种气候变暖的不均衡性是否会给草原生态系统土壤微生物群落带来显著的影响是我们所关注的问题之一。在第二章中，于多伦典型草原设置了对照、白天增温、夜间增温和全天增温处理，处理时间起始于2006 年5 月，并通过磷脂脂肪酸和BIOLOG 分析方法分别对土壤微生物的群落多样性和碳源利用能力（即功能多样性）进行分析。结果表明，不同增温处理对土壤微生物群落组成的影响均不显著，而夜间增温对土壤细菌群落的碳源利用能力具有显著的促进作用。这说明土壤微生物群落结构对短期增温处理的响应要滞后于功能的响应，而功能上的响应又首先出现在细菌群落，并且这种响应表现为白天增温和夜间增温的非加和效应。 气候变暖往往与降雨的变化相伴而生，而水分又是半干旱典型草原重要限制因子，因此探讨降雨的变化对土壤微生物的影响有助于更深入的了解土壤微生物对气候变暖的响应。在第三章中，分别设置了对照、增温、夏季增雨及增温×夏季增雨处理，处理时间起始于2005 年4 月，并同样分析了土壤微生物的群落组成和功能多样性。结果表明，增温和夏季增雨对土壤微生物群落结构和功能的影响具有明显的一致性，二者均降低了革兰氏阴性菌的相对含量，并且促进了细菌群落的碳源利用能力。增温和增雨在影响细菌群落结构（即，革兰氏阴性菌与阳性菌之比）上具有一定程度的交互效应。 陆地生态系统生产力普遍受到土壤氮素的限制，由于人类活动的干扰，尤其是农业生产和化石燃料燃烧，使土壤氮素含量增加，改变土壤理化环境和地上植物群落，这将直接或间接地影响土壤微生物群落结构和功能。就已有的研究结果来看施氮究竟如何影响土壤微生物群落尚无定论。第四章主要是针对相关研究结果上的分歧，在2003 年设置的0-64 g N m-2 yr-1 的指数施氮梯度实验上进行土壤理化因子、微生物量、净氮矿化和微生物碳源利用能力的分析。结果表明，土壤微生物群落对施氮的响应存在一个介于16 和32 g N m-2y-1 最优施氮量，即低于最优施氮量施氮处理表现为对土壤微生物的促进作用，而过高的施氮量则表现为抑制作用。这一结果说明施氮量是影响土壤微生物对施氮处理做出响应的重要方面之一，有助于解释目前相关研究中出现的结果分歧。 第五章的研究则是考虑了地形和火烧这两个草原生态系统普遍存在的干扰因素，比较分析二者与施氮处理对土壤微生物群落结构的影响。实验设置在多伦典型草原一个坡度为15﹪的南向阳坡，坡上坡下分别设置对照、施氮和火烧处理，处理的起始时间为2005 年4 月。结果表明，土壤微生物群落结构存在地形上的显著差异，表现为坡下以细菌类群占优势，而坡上真菌类群的相对优势较大;火烧对土壤微生物群落结构的影响显著，并表现出明显的地形上的差异，即坡下微生物对火烧的响应敏感性要高于坡上;而短期的施氮处理对土壤微生物群落结构的影响不显著。第六章的研究主要是针对增温、施氮和增温×施氮处理对土壤微生物群落结构和功能的影响，处理时间起始于2006 年5 月。结果表明，土壤微生物群落结构和功能年际变化显著;增温和施氮对土壤微生物的影响均不显著，但增温复合施氮处理中的土壤微生物群落结构表现出一定的响应趋势。

Distribution, transformation, and long-term accumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in different tissues of fish and piscivorous birds

The present study monitored 10-year-old fish and piscivorous birds from sites contaminated for many Stars. The data reflected the results of actual, long-term environmental exposures, The results demonstrate that different tissues of fish have quite different concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), The concentration order of PCDD/F within fish is liver congruent to egg congruent to intestines kidney congruent to hearts gill congruent to bladders > muscle > brain. The concentration order of PCDD/F within piscivorous birds was livers egg congruent to hearts muscle congruent to stomachs brain, The results obtained also demonstrate that the accumulation patterns of piscivorous birds and fish are quite different. The tissues of fish and piscivorous birds have different capacities for bioaccumulation and biotransformation of PCDD/F; variable proportions of TEQs were also found throughout their bodies. In fish, toxic equivalency quotient (TEQ): PCDD/F ratios in various tissues ranged from 0.01 to 0.07, whereas in birds the ratios ranged from 0.07 to 0.43. If the concentrations are normalized with lipid content, the results vary less. The effect of different lipid properties is obvious in the case of brain tissue, which is richer in phospholipids. (C) 2000 Academic Press.

Electro-mass olfactory multi-sensor (EMMS)

For an olfactory sensor or electronic nose, the task is not only to detect the object concentration, but also to recognize it. It is well known that all the elements can be identified by their charge to mass ratio e(+)/m. We tried to imitate this principle for molecular recognition. Two kinds of sensors are used simultaneously in testing. One is quartz crystal microbalance (QCM) for detecting the change in mass, the other is interdigital electrode (IE) for detecting the change in conduction, as an electro-mass multi-sensor (EMMS). in this paper, the principle and the feasibility of this method are discussed. The preliminary results on the recognition of alcohol by EMMS coated with lipids are presented. Meanwhile, the multi-sensor can also be used as an instrument for research on some physico-chemistry problems. The change in conduction of coated membrane caused by one absorbed molecule is reported. It is found that when a QCM is coated with membrane, it still obeys the relationship Delta F (frequency change of QCM) = K Delta m (mass change of absorbed substance) and the proportional coefficient, K, depends not only on quartz properties but also on membrane characteristics as well. (C) 2000 Elsevier Science S.A. All rights reserved.

Effects of molecular structures on the olfactory responses of phospholipid membranes to four alcohols

In order to understand the relationship between phospholipid molecular structures and their olfactory responses to odorants, we designed and synthesized four phosphatidylcholine analogues with different long hydrocarbon (CH) chains and selected three natural phospholipids with different head-groups. By using interdigital electrodes (IEs) as olfactory sensors (OSs), we measured the responses of the Ifs coated with these seven different lipid membranes to four alcohol vapors in a gas flow system. The Ifs voltage changes were recorded and the voltage-relative saturate vapor pressure (V-P/P degrees) curves were also plotted. It was found that with a methyl (-CH3) placed at the C-8 position in the 18-carbon chain, the olfactory responses could be improved about ten times and with conjugated double bonds (C=C) in the long chains, the sensitivity could be increased by 3 similar to 4 orders of magnitude. As to head-groups, choline is preferred over ethanolamine and serine in phospholipid structures in terms of high olfactory sensitivity: These results are expected to be useful in further designing and manufacturing lipid-mimicking OSs. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.

三价金属离子（AE~(3+)、Al~(3+)）及其配合物与磷脂双分子膜的作用研究

本文用二维核磁共振、富利叶变换拉曼光谱和差示扫描量热等方法研究了：1）稀土离子与柠檬酸配体的溶液配位行为，并用顺磁位移试剂的方法计算了该条件下的配合物形成稳定常数；2）稀土离子及其配合物与不同种类的磷脂分子的作用；3）二氧化硅和柠檬酸铝与DPPC脂质体的作用。

Electro-mass olfactory multi-sensor (EMMS)

For an olfactory sensor or electronic nose, the task is not only to detect the object concentration, but also to recognize it. It is well known that all the elements can be identified by their charge to mass ratio e(+)/m. We tried to imitate this principle for molecular recognition. Two kinds of sensors are used simultaneously in testing. One is quartz crystal microbalance (QCM) for detecting the change in mass, the other is interdigital electrode (IE) for detecting the change in conduction, as an electro-mass multi-sensor (EMMS). in this paper, the principle and the feasibility of this method are discussed. The preliminary results on the recognition of alcohol by EMMS coated with lipids are presented. Meanwhile, the multi-sensor can also be used as an instrument for research on some physico-chemistry problems. The change in conduction of coated membrane caused by one absorbed molecule is reported. It is found that when a QCM is coated with membrane, it still obeys the relationship Delta F (frequency change of QCM) = K Delta m (mass change of absorbed substance) and the proportional coefficient, K, depends not only on quartz properties but also on membrane characteristics as well. (C) 2000 Elsevier Science S.A. All rights reserved.

镉暴露下鱼体磷脂的代谢组学研究及安全评价

食品安全一直是世界各国密切关注的社会问题，直接关系人民群众的身体健康和社会稳定。代谢组学已广泛应用于毒理学机制研究、药物安全性评价等领域。将代谢组学技术应用于食品安全评价领域是一项有益的探索研究。目前我国许多水域镉含量超标，导致鱼类等水产品对镉的蓄积，对人体膳食健康造成威胁。 本文以鲫鱼为受试动物，开展室内水箱养殖实验，设定50g•L-1、500g•L-1两个镉浓度水平，共养殖25天，其中暴露期20天和净化期5天。通过镉含量测定和鱼肉磷脂代谢组学分析得到以下结论： 1）以暴露浓度、暴露时间、鱼体组织部位为因素，发现了鲫鱼对水环境中镉的积累和分布规律； 2）针对鱼肉开展磷脂代谢组学分析，①定性分析，通过质谱图解析基本确认了鱼肉中主要的磷脂分子的脂肪酸组成。②定量分析，采用HPLC定量分析暴露0天（K组）、10天（B组）、20天（D组）共计30个鱼肉样本中的磷脂酰胆碱（PC）含量， 发现K组与B组、B组与D组之间有显著性差异（P＜0.05），K组与D组无显著性差异。表明暴露10天后PC含量普遍低于正常水平（暴露0天），暴露20天后PC含量基本恢复到正常水平。③模式识别分析，PLS-DA主成分分析可有效识别K、B、D三组样本。 3）分别从限量标准、膳食安全风险评估两个角度评价了鱼肉膳食安全风险。通过PC定量分析和主成分分析，发现鱼肉中PC总量可以作为指示鲫鱼受到镉暴露的生物标示物；通过磷脂代谢图谱与鱼肉镉含量PLS拟合模型分析有效表征和量化了鱼肉磷脂对镉暴露的代谢响应，探索性提出借助拟合模型，通过磷脂代谢图谱分析预测鱼肉样本的镉含量。 4）在食品安全风险评价方面，建议采用限量标准、膳食摄入量、代谢组学识别和模型预测分析等相结合的手段，对传统风险评估体系在继承的基础上加以科学性的扩充和完善。

Interaction between alpha-actinin and negatively charged lipids membrane investigated by surface plasmon resonance and electrochemical methods

alpha-Actinin has been shown to be capable of interacting with some special membrane phospholipids directly, which is important for its function. In this study, hybrid bilayer membranes composed of negatively charged lipids are constructed on the surface plasmon resonance gold substrate and on the gold electrode, respectively, and the interaction between alpha-actinin and negatively charged lipids membrane is investigated by surface plasmon resonance, cyclic voltammetry and electrochemical impedance spectroscopy methods. alpha-Actinin is proved to be able to interact with the negatively charged lipids membrane directly. It can also insert at least partly into the membrane or lead to some defect or lesion in the membrane, which increase the permeability of the membrane. This study would bring some insight on the interaction between the alpha-actinin and the cell membranes in vivo.

Daunomycin binding to detergent micelles: A model system for evaluating the hydrophobic contribution to drug-DNA interactions

The interaction of daunomycin with sodium dodecyl sulfate and Triton X-100 micelles was investigated as a model for the hydrophobic contribution to the free energy of DNA intercalation reactions. Measurements of visible absorbance, fluorescence lifetime, steady-state fluorescence emission intensity, and fluorescence anisotropy indicate that the anthraquinone ring partitions into the hydrophobic micelle interior. Fluorescence quenching experiments using both steady-state and lifetime measurements demonstrate reduced accessibility of daunomycin in sodium dodecyl sulfate micelles to the anionic quencher iodide and to the neutral quencher acrylamide. Quenching of daunomycin fluorescence by iodide in Triton X-100 micelles was similar to that seen with free daunomycin. Studies of the energetics of the interaction of daunomycin with micelles by fluorescence and absorbance titration methods and by isothermal titration calorimetry in the presence of excess micelles revealed that association with sodium dodecyl sulfate and Triton X-100 micelles is driven by a large negative enthalpy. Association of the drug with both types of micelles also has a favorable entropic contribution, which is larger in magnitude for Triton X-100 micelles than for sodium dodecyl sulfate micelles.

A study on the interaction between ibuprofen and bilayer lipid membrane

Ibuprofen is a well-known nonsteroidal anti-inflammatory drug, which can interact with lipid membranes. In this paper, the interaction of ibuprofen with bilayer lipid membrane was studied by UV-vis spectroscopy, cyclic voltammetry and AC impedance spectroscopy. UV-vis spectroscopy data indicated directly that ibuprofen could interact with lipid vesicles. In electrochemical experiments, ibuprofen displayed a biphasic behavior on bilayer lipid membrane supported on a glassy carbon electrode. It could stabilize the lipid membrane in low concentration, while it induced defects formation, even removed off bilayer lipid membrane from the surface of the electrode with increasing concentration. The mechanism about the interaction between ibuprofen and supported bilayer lipid membrane was discussed.

Self-assembled monolayers of thiols on gold electrodes for bioelectrochemistry and biosensors

Monolayers of biological compounds including redox proteins and enzymes, and phospholipids have been immobilized on a gold electrode surface through self-assembling. These proteins and enzymes, such as cytochrome c, cytochrome c oxidase and horseradish peroxidase (HRP), immobilized covalently to the self-assembled monolayers (SAMs) of 3-mercaptopropionic acid on a gold electrode, communicate directly electrons with the electrode surface without mediators and keep their physiological activities. The electron transfer of HRP with the gold electrode can also be mediated by the alkanethiol SAMs with electroactive group viologens on the gold electrode surface. All these direct electrochemistries of proteins and enzymes might offer an opportunity to build a third generation of biosensors without mediators for analytes, such as H2O2, glucose and cholesterol. Monensin and valinomycin have been incorporated into the bilayers on the gold electrode consisting of the SAMs of alkanethiol and a lipid monolayer, which have high selectivity for monovalent ions, and the resulting Na+ or K+ sensor has a wide linear range and high stability. These self-assembly systems provide a good mimetic model for studying the physiological function of a membrane and its associated enzyme. (C) 1997 Elsevier Science S.A.