Physicochemical and Cytochemical Investigations on the Binding of Ethidium and Acridine Dyes to DNA and to Organelles in Living Cells

Ethidium and acridine dyes are classical model substances for studying the binding of small, pharmacologically active molecules to DNA. Intercalation between the DNA base pairs is nearly always proposed as the most important type of binding. According to our investigations, however, there is a second type of binding, which also occurs when the concentration of the bound molecules is low and will be referred to here as external or preintercalative binding. The experimental binding isotherms show that the binding constant for intercalation K_S1 is considerably smaller than that for external binding K_S2 (K_S1 > K_S2). This surprising result is not due to the binding enthalpy (ΔH ≈ ΔH) but to the binding entropy (ΔS > ΔS). Electrostatic interactions between the dye and the DNA represent the most important contribution to both types of binding; they are supplemented by hydrogen bonds and hydrophobic interactions. The behavior of a substance in living cells, however, cannot be reliably predicted from its in vitro binding to DNA. Very few substances are bound to the DNA of the nuclear chromatin in cell culture; for example, dyes often accumulate instead in the lysosomes. In some cases the dye binds specifically and very efficiently to the mitochondria of the living cell, especially to the mitochondrial membranes, the sites of oxidative phosphorylation.     

Active transport of Na + and K + through animal cell membranes

The transport of Na⁺ out of the cell and K⁺ into the cell against a concentration gradient is catalyzed by a (Na⁺ + K⁺)-activated ATPase. The way in which the cations pass through the cell membrane has not yet been elucidated. Studies on the ATP hydrolysis revealed a Na⁺-dependent phosphorylation of the enzyme protein; the conformation of the enzyme also appears to change. The energy required for transport of the cations against their concentration gradients is probably provided by K⁺-dependent hydrolysis of the enzyme-bound phosphate. The enzyme can synthesize ATP from inorganic phosphate and ADP on reversal of the cation concentration gradient. By keeping the enzyme in a particular conformation, the cardiac glycoside ouabain specifically inhibits the Na⁺ pump.     

傅里叶变换红外光谱用于胆囊癌细胞及其细胞核结构的基础研究

应用傅里叶变换红外光谱(FTIR)对体外培养胆囊癌细胞、细胞核进行检测,对照胆囊癌组织光谱特征,研究胆囊癌细胞株及细胞核的光谱表现;为红外光谱法诊断胆囊癌奠定细胞学基础。应用美国Nicolet(尼高力)公司5700-Ⅱ型红外光谱仪,组织标本放置于OMNIC采样器表面进行检测,记录红外光谱;体外培养胆囊癌细胞株(GBC-SD)及提取的细胞核涂于欧米采样器表面进行红外检测,记录红外光谱,得到时间轴上体外培养细胞株及细胞核的光谱图;选择特征性光谱与胆囊癌组织光谱进行比对。结果发现胆囊癌细胞株红外光谱特征与相应癌组织光谱特征存在异同。从而可得出结论：将体外培养肿瘤细胞株及提取的肿瘤细胞核,进行FTIR测定是行之有效的细胞红外光谱检测手段,能得到体外培养细胞的红外谱图;胆囊癌组织所表现的红外光谱特征具有胆囊癌细胞本身的红外光谱特征,同时也具有组织自身的复杂特点;FTIR为应用于胆囊癌的定性诊断提供了更加丰富的细胞学基础。     

准分布式光纤Bragg光栅传感器在微生物燃料电池温度场测量中的应用

微生物燃料电池(MFC)在近些年得到了迅猛了发展,尤其是MFC具有产电且同时处理废水的效果,引起了世界各国科学家的高度关注。如何提高MFC产电效率的问题一直是MFC的研究重点,其中温度是影响微生物活性的一个重要因素,进而影响MFC的产电效率。为了能够更好地了解温度场与MFC的产电效率的关系,本文采用准分布式光纤Bragg光栅(FBG)阵列,对MFC阳极室内温度场分布进行实时测量。实验表明:该方法能够测量MFC运行阶段阳极室内温度场分布,反应前后温度差3-4℃,该方法为研究MFC内温度与产电效率的关系提供一种新的手段。     

Device for aeration and mixing of cell and organelle suspensions during NMR experiments

A device for aeration and mixing of cell or organelle suspensions in a vertical bore NMR magnet is described. Multiple external sensors (e.g., ion-selective electrodes) may be immersed in the suspension within the bore of the magnet. The sensors are positioned to avoid noise due to contact with gas bubbles and proximity to the probe head. The required sample volume is minimised. The modular design of components permits the use of the device in magnets of various internal dimensions, or with probe heads of different sample tube diameter, by modification of the simpler components of the assembly.     

In vivo Cellular Uptake,Degradation, and Biocompatibility of Polyelectrolyte Microcapsules

Polyelectrolyte microcapsules are made by layer‐by‐layer (LbL) coating of a sacrificial template, followed by decomposition of the template, to produce hollow microcapsules. In this paper, we report on the in vivo cellular uptake, degradation and biocompatibility of polyelectrolyte microcapsules produced from alternating dextran sulphate and poly‐L‐arginine layers on a template of calcium carbonate microparticles. We show that a moderate tissue reaction is observed after subcutaneous injection of polyelectrolyte microcapsules in mice. Within sixteen days after subcutaneous injection, most of the microcapsules are internalized by the cells and start to get degraded. The number of polyelectrolyte layers determines the stability of the microcapsules after cellular uptake.     

Numerical solutions of a model for the propagation of a surface-catalysed flame in a tube

Numerical simulations of a surface-catalysed flame in a tubeare performed, corresponding to an experiment where a premixedfuel is fed into a tube whose inner surface is coated with acatalyst. In these experiments, subsequent to ignition, a reactionwave can be seen as a red-hot region which propagates back alongthe tube towards the inlet, and is due to low temperature combustionoccurring only on the inner surface of the tube where the catalystis present. The solutions of a mathematical model for this behaviourshow that initial-value problems do indeed result in such steadilypropagating waves. The numerically obtained wave speeds andsteady solution are compared to a previous large Damköhlernumber (D_a) asymptotic analysis using a simple reaction ratemodel, and agreement is very good even for moderately largevalues of D_a. However, for such Damköhler numbers, thewave speeds are found to be much larger than observed experimentally.Indeed, the simulations show that O(1) values of D_a are requiredto obtain the lower experimental wave speeds. Nevertheless,the wave speeds as a function of flow rate through the tubedo not agree well with the preliminary experimental resultsfor any choice of the parameters. A more realistic, Arrheniusreaction rate model is then considered. The Arrhenius modelpredicts a rapid change in temperature at the wave front, inmuch better agreement with the experiments than for the simplerreaction model.     

基于1,8-萘酰亚胺的半胱氨酸荧光探针的合成及在生物成像方面的应用

设计合成了一种用于检测半胱氨酸的新型荧光探针乙二醛(N-羟乙基-1,8-二甲酰亚胺-4-萘基)单腙(NAD),该荧光探针对半胱氨酸表现出较高的灵敏度和选择性.当半胱氨酸加入NAD溶液中,会形成分子内氢键,抑制C■N的异构化,导致荧光增强.此外,探针NAD可应用于细胞内半胱氨酸的检测,表明该类型探针在生物检测应用方面具有较大的潜力.     

人白细胞介素12双亚基共表达pVAX1-IRES-hIL12载体的构建与表达

目的构建下游可以共表达人白细胞介素12(hIL12)双亚基的双顺反子真核表达载体pVAX1-IRES-hIL12。方法通过搭桥PCR获得人白细胞介素12P35及P40双亚基的融合基因P35-F2A-P40,插入DNA疫苗载体pVAX1-IRES的下游,瞬时转染293-T细胞,ELISA检测融合基因的表达。结果酶切鉴定和序列分析表明融合基因与设计完全一致,融合基因在体外细胞培养液检测中获得分泌表达。结论该载体的成功构建可以为肿瘤基因疫苗研制提供免疫增效载体。     

Measuring the External Quantum Efficiency of Two‐Terminal Polymer Tandem Solar Cells

Tandem configurations, in which two cells are stacked and connected in series, offer a viable approach to further increase the power conversion efficiency (PCE) of organic solar cells. To enable the future rational design of new materials it is important to accurately assess the contributions of individual subcells. Such accurate measurement of the external quantum efficiency (EQE) of the subcells of two‐terminal organic or polymer tandem solar cells poses specific challenges, caused by two characteristics of these cells, i.e. a sub‐linear light intensity dependence of the current and a field‐assisted charge collection. These properties necessitate that EQE experiments are carried out under representative illumination conditions and electrical bias to maintain short‐circuit conditions for the addressed subcell. We describe a method to determine the magnitudes of the bias illumination and bias voltage during EQE measurements, based on the behavior of single junction cells and optical modeling. The short‐circuit current densities of the subcells obtained by convolution of the EQE with the AM1.5G solar spectrum are consistent with those obtained from optical modeling and correctly predict the current density–voltage characteristics of the tandem cell under AM1.5G conditions.