Steady-state electrolysis at a grooved or ridged plane

This study concerns an infinite plane whose smoothness is marred by a single defect: either a groove or a ridge. The blemished plane serves as an electrode supporting a diffusion-controlled steady-state process. By using a convenient coordinate transformation, the local current density at all points on the surface is determined exactly. The results are found to confirm intuitive expectations. Thus, compared with normal values on the plane remote from a groove, the electron transfer rate is diminished within the groove but enhanced along its margins. Similarly, an abnormally large transfer rate is encountered high on the ridge but the rate is subnormal on its lower flanks. The total current is demonstrated to be unchanged by the presence of the blemish. Received: 27 September 1996 / Accepted: 11 March 1997     

Spectroscopic and Binding Properties of Berberine to DNA and Its Application to DNA Detection

Berberine(BER) binds to the double helical DNA with a high affinity There is only a much smaller hypochromism and no shifts in the absorption spectra when BER binds to calf thymus DNA(CT DNA) The fluorescence yields increase dramatically when BER binds to DNA, with no shifts in the emission maximum. These spectral changes are in contrast to the behavior observed with many fluorescent intercalates Groove binding rather than intercalation was suggested to be the cause of these spectral changes. Consistent with groove binding, for polyamide anion quenching studies showed that the magnitude of K_sv of the bound BER was higher than that of the free BER. The addition of salt to the solution releases the DNA-bound drug action from the groove and causes a decrease in the fluorescence yield. The results of all above studies proved the groove binding of BER to DNA. The large fluorescence enhancements observed when BER binds to DNA and the poor fluorescence yield of BER in the absence of DNA can be used for sensitive detection of DNA The linear concentration range was 0–20μg/ml The limit of detection for CT DNA was 12 ng/ml     

Sensitive Nucleic Acid Detection at NH2‐MWCNTs Modified Glassy Carbon Electrode and its Application for Monitoring of Gemcitabine‐DNA Interaction

An electrochemical dsDNA nanobiosensor was fabricated using amino‐functionalized multi walled carbon nanotubes modified glassy carbon electrode (NH₂fMWCNTs/GCE) for the sensitive detection of DNA bases and electrochemical monitoring of drug‐DNA interaction. The influence of functional groups on MWCNT was studied by MWCNT functionalized with NH₂ (NH₂fMWCNTs) and COOH (COOHfMWCNT) groups based on the signal of DNA bases. The modified electrodes were characterized by scanning electron microscopy. One layer of calf thymus double stranded deoxyribonucleic acid (ct‐dsDNA) was immobilized onto the NH₂fMWCNTs/GCE (dsDNA/NH₂fMWCNTs/GCE). The dsDNA/NH₂fMWCNTs/GCE were used to investigate the interaction between the dsDNA and the anticancer drug gemcitabine by differential pulse voltammetry in acetate buffer of pH 4.70. For the confirmation of interaction, the lowering in intensity of the current signals of guanine and adenine was considered as an indicator. Electrochemical impedance spectroscopy studies were performed for the comparison of the modified surfaces. In order to define and visualize the interaction mechanism between gemcitabine and dsDNA/NH₂fMWCNTs/GCE at the molecular level, in silico methods including docking and molecular dynamics simulations were employed.     

对称面形光栅TE模的衍射特性

本文采用耦合波方法计算了对称面形光栅的衍射效率,分析了光栅截面面形为正弦、三角形、矩形、梯形光栅衍射效率与光栅周期、沟槽深度的关系,计算了光栅的峰值衍射效率。理论计算表明:合理地选择光栅周期、沟槽深度,对称面形光栅都可以达到很高衍射效率,接近100%;光栅的峰值衍射效率基本出现在Bragg衍射且光栅的周期等于衍射波长时。     

Synthesis,characterization and DNA interaction studies of a new platinum(II) complex containing caffeine and histidine ligands using instrumental and computational methods

A new Pt(II) complex, [Pt(Caff)(His)(Cl)] (Caff is Caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) and His is l-Histidine), was synthesized and characterized using different physicochemical methods. The interaction of this complex with calf thymus DNA (ct-DNA) was investigated by absorption, emission, circular dichroism (CD), and viscosity measurements and molecular docking techniques. The calculated binding constant, K_b, was 5.3 × 10³ M^?1. In fluorimetric studies, the enthalpy and entropy of the reaction between the complex and ct-DNA showed that the reaction is exothermic (?H = ?184.07 kJ mol^?1, ?S = ?551.97 J mol^?1 K^?1). CD spectra of DNA in the presence of different amounts of the complex showed little changes in both the negative and positive band intensities, which imply a non-intercalative mode between the DNA and the platinum complex. Furthermore, the study of molecular docking also indicated that the complex binds to DNA via a groove binding mode.     

溴鼠灵与DNA作用机制的光谱研究

农用化学物质残留可能会与DNA结合形成加和物,从而对动物和人类造成危害。文章利用紫外光谱和荧光光谱研究了溴鼠灵(BDF)与小牛胸腺DNA(ct-DNA)的作用机理。结果表明,低浓度的ct-DNA可使BDF的吸收光谱发生减色,ct-DNA对BDF的稳态荧光有明显的的猝灭作用,属于静态猝灭方式,27 ℃时K_SV=1.21×104 L·mol-1;根据热力学参数推测BDF与ct-DNA之间的相互作用主要是范德瓦耳斯力作用;猝灭试验发现ct-DNA对BDF无明显保护作用;离子强度改变时,BDF/ct-DNA体系的荧光强度也随之改变;ct-DNA对β-CD/BDF包络物的荧光也有猝灭,但猝灭程度比游离的BDF有所降低,表明β-CD对BDF具有保护作用,也说明BDF与ct-DNA或β-CD的结合具有竞争性。各试验结果一致表明BDF与ct-DNA之间主要是以沟区结合方式发生作用。另外,试验结果也表明BDF与ct-DNA之间还存在静电作用。范德瓦耳斯力和静电作用的共同作用,为BDF在沟区与DNA的相互结合提供了更好条件。     

Synthesis of a hypocrellin B-polyamide conjugate as DNA-targeting photosensitizer

A new hypocrellin B （HB） derivative bearing a bispyrrolecarboxamide-containing side chain was synthesized, which presents improved absorptivity in phototherapeufic window than HB and affinity feature towards dsDNA.     

环斑铂立体异构体与DNA的作用

研究了环斑铂的三种立体异构体（RSRR和SS）与小牛胸腺DNA的作用．用等温滴定量热法（ITC）测得三种化合物与DNA在298．15K时相互作用的摩尔烙变分别为-1．1,－7．2和16KJ·mol－1;差示扫描量热法（DSC）结果证实三种化合物与DNA作用使得其解链温度分别升高3．56,7.66和8．53K;而圆二色性波谱研究（CD）则显示出在室温时三种化合物与DNA间的作用使得其摩尔椭圆度发生了不等的微弱变化;核磁共振波谱法（NMR）结果告诉我们在室温时DNA的加入未使SS-环斑铂1H谱的化学位移及峰型出现明显的改变．综合热力学及波谱实验结果,对环斑钥立体异构体与DNA作用及结合的方式进行了讨论．     

Computer simulation of the binding of quinocarcin to DNA. Prediction of mode of action and absolute configuration

Summary Computer-based models were derived for the covalent and noncovalent binding of the antitumor antibiotic quinocarcin to a representative DNA segment, d(ATGCAT)₂. They showed that a mode of action, involving opening of the oxazolidine ring to give an iminium ion, followed by initial noncovalent binding in the minor groove and subsequent alkylation of the 2-amino group of guanine, was rational and attended by favorable interaction energies in each step. The best model had the aryl ring of quinocarcin lying in the 3 direction from the covalent binding site and anR configuration at the carbon involved in covalent bond formation. It also showed that the preferred absolute configuration for quinocarcin was the reverse of that arbitrarily assigned in the literature.     

新型多吡啶配体的设计及其对配合物与DNA作用机制的影响

近年来 ,以钌 ( )多吡啶配合物为探针研究 DNA的结构已成为生物无机化学领域中的一个热点[1,2 ] .这些配合物由于热力学稳定性好 ,光化学和光物理信息丰富 ,在研究 DNA内部的电子转移和Fig.1　 Structures of the ligandsDNA的结构识别等方面均有重要的作用[3～ 7] .在配合物与 DNA的相互作用中 ,配合物的形状、大小以及中心离子电荷等都有一定的影响[8] ,其中 ,配合物的形状起着至关重要的作用 ,与 DNA的形状匹配的配合物与DNA的结合较强 .这些配合物中通常含有平面性较大的芳香环配体 ,可插入到 DNA的碱基对之间 ,并与 DNA具有…