吖啶橙-罗丹明B二聚体能量转移体系在DNA测定中的应用及机理研究

首次研究了吖啶橙 罗丹明B二聚体能量转移体系作为荧光探针用于DNA的测定 ,并对其机理进行了探讨。用于鲱鱼精DNA和小牛胸腺DNA的测定 ,线性范围分别为 0 33～ 1 33mg·L- 1 ,0 33～ 3 33mg·L- 1 ,检测限分别为 1 6 3× 10 - 3mg·L- 1 ,1 5 2× 10 - 3mg·L- 1 。对 1 0 0mg·L- 1 鲱鱼精DNA和小牛胸腺DNA的测定 ,相对标准偏差分别为 2 4 %和 2 0 %。     

二溴羟基卟啉与核酸相互作用的光谱行为研究

研究了meso-4(3,5-二溴-4-羟基苯基)卟啉(T(DBHP)P)与小牛胸腺DNA (ct DNA)相互作用的光谱行为,探讨了以T(DBHP)P作为光谱探针测定核酸的最佳条件及作用机理。在 pH 4.92 HAc-NaAc缓冲液中,T(DBHP)P在最大吸收波长425 nm处的吸收峰强度显著下降,且下降程度与ct DNA含量呈线性关系,ct DNA含量在0.20～1.80 μg·mL-1范围内符合比尔定律,检出限为0.024 μg·mL-1。实验中发现Tween-80微乳液的加入能显著增加体系的灵敏度。同时,用摩尔比法测定了DNA与卟啉的结合数为21,并初步探讨了反应机理。     

吖啶橙共振光散射法测定脱氧核糖核酸

研究了吖啶橙与DNA作用的共振散射光谱,发现在pH 11的碱性溶液中痕量核酸对吖啶橙的共振散射光产生增强作用,且增强程度与核酸浓度之间有良好的线性关系。据此建立了测定核酸的高灵敏共振光增强分析方法。其最大散射波长均位于324 nm处,测定鱼精DNA(fs DNA)的线性范围是3.1×10-8～7.3×10-6 g·mL-1,检测限20.5 ng·mL-1,测定小牛胸腺DNA(ct DNA)的线性范围是7.5×10-8～9.8×10-6 g·mL-1,检测限20.8 ng·mL-1。该方法简单,操作方便,选择性好,灵敏度高,用于合成样品的测定结果满意。     

原子簇化合物十羰基二锰与DNA相互作用

采用紫外-可见吸收光谱、荧光光谱等对十羰基二锰簇合物与小牛胸腺DNA的作用方式进行了研究,结果发现在该簇合物存在下,DNA的紫外吸收光谱产生了明显的增色效应。荧光光谱研究表明DNA的荧光强度随着羰基锰簇合物的加入其荧光强度明显增加,说明羰基二锰簇合物与DNA之间存在着相互作用,作用方式可能为嵌插。     

鬼臼酰肼金属Ni(Ⅱ), Co(Ⅱ), Zn(Ⅱ)配合物与DNA分子作用机制的研究

在pH 7.08 Tris缓冲溶液中,采用粘度测定、电子吸收光谱、凝胶电泳和溴化乙锭荧光分析法研究了鬼臼酰肼(hydrazide-podophyllic,HDPP)NiⅡ, CoⅡ, ZnⅡ金属配合物与小牛胸腺DNA的作用机制,探讨了作用模式。结果发现,当加入一定量的DNA时,配合物的电子吸收光谱的最大吸收峰产生减色效应,同时,DNA也能较大程度地猝灭配合物体系的荧光强度。配合物都能引起DNA粘度的略微增加和将超螺旋DNA切割得到缺刻DNA。所有这些研究表明配合物可能与DNA发生了相互作用,其中镍和钴配合物与DNA之间主要以插入方式相结合;而锌配合物与DNA之间的结合方式为部分插入;求出了三种鬼臼酰肼金属配合物与DNA的结合常数。     

解析动态光谱的奇异值分解最小二乘法的改进

本文改进了处理动态光谱的奇异值分解最小二乘法（SVDLS），通过对模拟的蛋白质二级结构的动态圆二色谱和小牛胸腺DNA在电化学过程中动态紫外光谱的分析，表明该方法不仅给出动态过程中所包含的组分数，而且可同时获得各组分的光谱和各组分分数的分布曲线，是多种动态光谱数据处理的有效的无模型方法。     

硫堇与DNA分子作用机理的光谱研究

用紫外-可见吸收光谱、荧光光谱、圆二色谱和光电子能谱等光谱方法研究了硫堇(TH)与小牛胸腺DNA(CT-DNA)的作用机理。实验结果表明,在pH 7.2的磷酸盐缓冲溶液中, TH与CT-DNA之间的作用方式以嵌入作用为主,嵌入作用使TH的紫外最大吸收峰强度减小,且峰位发生红移。由紫外光谱实验结果线性拟合求得TH与CT-DNA的表观结合常数K＝1.45×104 L·mol-1。荧光光谱实验结果表明：TH与CT-DNA的嵌入作用使TH的荧光发生强烈猝灭,猝灭常数K_SV为1.01×104 L·mol-1。嵌入作用位点主要发生在CT-DNA的鸟嘌呤(G)-胞嘧啶(C)碱基序列富集区。通过对TH的光电子能谱中N,S原子的结合能变化分析,TH分子以杂环上S原子端与CT-DNA的G-C碱基对结合,两者的相互作用对CT-DNA的二级结构构象产生影响。     

阿霉素与DNA作用的共振光散射研究及在DNA分析中的应用

研究了抗癌药物阿霉素与DNA相互作用的吸收光谱、荧光光谱和共振光散射光谱,发现阿霉素与DNA相互作用产生强烈增强的共振光散射信号,共振光散射技术在研究DNA与阿霉素的相互作用时,其灵敏度远远高于吸收光谱和荧光光谱。DNA与阿霉素作用在322与564 nm处产生两个共振散射峰,在弱酸性条件下(pH 5.72),DNA的浓度在0～8.0 μg·mL-1范围内与散射强度呈良好的线性关系,对小牛胸腺DNA和鱼精子DNA的检出限分别为36.8和40.1 ng·mL-1。由此建立了一种选择性好,灵敏度高的DNA共振光散射分析方法。     

环丙氟沙星荧光探针对小牛胸腺DNA相互作用的研究

使用紫外和荧光光谱法研究了环丙氟沙星(CIF)和小牛胸腺DNA(ctDNA)之间的相互作用。在pH 7.0磷酸盐缓冲液中,CIF在270 nm激发和在420 nm处有很强的荧光发射。它们间的沟槽作用导致小牛胸腺ctDNA对CIF的荧光存在着很强的猝灭作用,猝灭常数为2.64×104 mol-1L(25 ℃)。利用ctDNA对CIF的荧光猝灭作用建立了核酸测定的新方法,线性范围为80 nmol·L-1～45 μmol·L-1,对25 μmol·L-1ctDNA的相对标准偏差为4.2％。     

桑色素-Ce(Ⅳ)体系共振光散射法选择性测定小牛胸腺DNA

研究了桑色素与Ce(Ⅳ)反应形成的络合物与DNA作用的共振光散射(RLS)特征,发现小牛胸腺DNA(ctDNA)或鲱鱼精DNA(hsDNA)的加入都能使桑色素-Ce(Ⅳ)体系在320 nm处的共振光散射峰增强。在最优条件下,RLS强度与ctDNA的浓度在0～25 μg·mL-1范围内呈良好的线性关系,检出限为0.3 μg·mL-1;但是RLS强度对hsDNA的浓度却没有线性响应。并且,由于RLS强度对hsDNA浓度的响应值大大低于同浓度的ctDNA,因此可用于hsDNA存在下对ctDNA的选择性测定。将该法用于4种合成样的测定,回收率在93.7%～108.4%之间。     

Evidence for a possible role of 3‐hydroxyanthranilic acid as an antioxidant

The reactions of 3‐hydroxyanthranilic acid (3‐OHAA) with N₃^?, NO₂^?, NO^?, CCl₃O₂^? , and OH^? radicals were examined using a pulse radiolysis technique mainly at pH 7. The bimolecular electron transfer from secondary one‐electron oxidants results in the formation of anilino radical (λ_max ? 380 nm). The rate constant for the reaction of N₃^? radical with 3‐OHAA at pH 7 was found to be 6.3 × 10⁹ dm³ mol^?1 s^?1. It was observed that the 3‐OHAA reacts with oxygen centered radicals. The repair rate constant for the electron transfer reaction from 3‐OHAA to guanosine radical and chlorpromazine cation radical was also examined using a pulse radiolysis technique. Kinetic studies indicate that 3‐OHAA may act as an antioxidant to repair free‐radical damage to above mentioned biologically important compounds. The rate constants of electron transfer from the 3‐OHAA to the guanosine and chlorpromazine radicals were determined. The one‐electron reduction potential for 3‐OHAA radical was found to be 0.53 ± 0.06 V versus NHE. Copyright © 2008 John Wiley & Sons, Ltd.     

光谱及电化学方法研究大黄酸与牛血清白蛋白的相互作用

采用荧光光谱、紫外光谱和圆二色光谱法并结合电化学方法,研究了大黄酸与牛血清白蛋白之间的相互作用。结果表明:大黄酸对牛血清白蛋白有较强的荧光猝灭作用且为静态猝灭,并计算得出不同温度下其结合常数(KA)与结合位点数(n)分别为:3.67×105,0.95(298 K);2.60×104,0.83(309 K)。由热力学参数确定它们间的作用力主要是静电引力,并依据F rster能量转移理论求得其结合距离为3.28 nm,同步荧光光谱及圆二色谱表明大黄酸对牛血清白蛋白的构象产生影响。     

Biophysical and electrochemical properties of Self-assembled noncovalent SWNT/DNA hybrid and electroactive nanostructure

DNA self-assembled hybrid nanostructures are widely used in recent research in nanobiotechnology. Combination of DNA with carbon based nanoparticles such as single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT) and carbon quantum dot were applied in important biological applications. Many examples of biosensors, nanowires and nanoelectronic devices, nanomachine and drug delivery systems are fabricated by these hybrid nanostructures. In this study, a new hybrid nanostructure has been fabricated by noncovalent interactions between single or double stranded DNA and SWNT nanoparticles and biophysical properties of these structures were studied comparatively. Biophysical properties of hybrid nanostructures studied by circular dichroism, UV–vis and fluorescence spectroscopy techniques. Also, electrochemical properties studied by cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, choronoamperometry and impedance spectroscopy (EIS). Results revealed that the biophysical and electrochemical properties of SWNT/DNA hybrid nanostructures were different compare to ss-DNA, ds-DNA and SWNT singly. Circular dichroism results showed that ss-DNA wrapped around the nanotubes through π-π stacking interactions. The results indicated that after adding SWNT to ss-DNA and ds-DNA intensity of CD and UV–vis spectrum peaks were decreased. Electrochemical experiments indicated that the modification of single-walled carbon nanotubes by ss-DNA improves the electron transfer rate of hybrid nanostructures. It was demonstrated SWNT/DNA hybrid nanostructures should be a good electroactive nanostructure that can be used for electrochemical detection or sensing.     

核苷酸和芳香酮的电子转移和质子转移反应研究

利用时间分辨的激光闪光光解方法在1∶1乙腈/水溶液中得到了4种核苷酸和芳香酮的瞬态吸收光谱,通过瞬态吸收光谱的变化研究了鸟苷酸、腺苷酸、胞苷酸、胸腺苷酸猝灭二苯甲酮、呫吨酮激发三重态的反应。由于实验中生成了抽氢自由基和负离子自由基,以及核苷酸正离子在水中的快速抽氢反应,推断出芳香酮和鸟苷酸、腺苷酸的反应机理是先发生电子转移后发生质子转移。而在芳香酮和胞苷酸、胸腺苷酸的反应中没有观察到相应的抽氢自由基和负离子自由基的瞬态吸收峰,由此推断出它们和胞苷酸、胸腺苷酸没有发生电子转移和质子转移反应。对瞬态吸收峰处的时间衰减曲线进行拟合得到了核苷酸猝灭芳香酮的速率常数,可以看到随着反应自由能变ΔG的增大,反应速率常数逐渐减小。     

Circular dichroism in laser-assisted short-pulse photoionization

A remarkable effect of circular dichroism, i.e., a difference in photoelectron spectra produced by right and left circularly polarized light in two-color multiphoton ionization of atoms, is predicted for the case when the atom is ionized by an extreme ultraviolet or x-ray femtosecond pulse in the field of a strong infrared laser pulse, both pulses being circularly polarized. We show that the sidebands formed in the spectra exhibit different circular dichroism often of different signs both in angle-resolved and angle-integrated experimental conditions. The effect can be used for detecting and measuring circular polarization of x rays in a spectral range where other methods are not effective.     

Sequence Dependent Ultrafast Electron Transfer of Nile Blue in Oligonucleotides

In this contribution we report studies on the nature of binding of nile blue (NB), a well known DNA intercalating drug, with three synthetic DNA oligonucleotides, (CGCAAATTTGCG)₂, (GCGCGCGCGCGC)₂ and (ATATATATATAT)₂. The nature of fluorescence quenching of the ligand upon complexation with the DNAs has been studied using steady state and picosecond-resolved optical spectroscopic techniques. The geometrical restriction on the probe in the DNA microenvironment is measured using picosecond-resolved rotational anisotropy measurements. Our experiments identify both non-specific electrostatic and intercalative modes of interaction of the probe with the DNAs at lower and higher DNA concentrations, respectively. This dual nature of binding is also confirmed through gel electrophoresis experiments. The nature of electron transfer (ET) reaction of GC base pairs with intercalated NB has also been explored. Competitive binding study reveals that binding affinity of the probe is higher with SDS micelles than with the DNAs within its structural integrity in presence of the micelles, as evidenced from circular dichroism (CD) measurements. The complex rigidity of NB with various DNAs and its fluorescence quenching with DNAs elucidate a strong recognition mechanism between NB and DNA.     

Room-temperature ferromagnetism in a II-VI diluted magnetic semiconductor Zn(1-x)Cr(x)Te

The magnetic and magneto-optical properties of a Cr-doped II-VI semiconductor ZnTe were investigated. Magnetic circular dichroism measurements showed a strong interaction between the sp carriers and localized d spins, indicating that Zn(1-x)Cr(x)Te is a diluted magnetic semiconductor. The Curie temperature of the film with x=0.20 was estimated to be 300+/-10 K, which is the highest value ever reported for a diluted magnetic semiconductor in which sp-d interactions were confirmed. In spite of its high Curie temperature, Zn(1-x)Cr(x)Te film shows semiconducting electrical transport properties.     

长春新碱与牛血清白蛋白相互作用研究

利用紫外、荧光和圆二色光谱研究了不同温度下长春新碱(VCR)与牛血清白蛋白(BSA)之间的相互作用。通过荧光猝灭数据算得在 296,303和310 K时,VCR与BSA的猝灭常数K_SV分别为2.0×104,1.7×104和1.5×104 L·mol-1,结合常数K_a分别为1.5×104,9.5×103和4.9×103 L·mol-1,结合位点数分别为0.978 6,0.949 0和0.891 1,表明VCR与BSA间具有较强的结合作用,但结合能随着温度的升高而降低,是形成复合物的静态猝灭。圆二色光谱 (CD)数据表明相互作用后BSA的二级结构发生了改变：BSA的α-螺旋的含量从33.5％下降到 29.7％,β-折叠的含量从13.6％升高到18.4％。通过Van′t Hoff方程,计算出热力学常数焓变(ΔH)和熵变(ΔS) 分别为：－62.7 kJ·mol-1和－129.38 J·（mol-1·K）－１,表明氢键和范德华力在VCR与BSA结合中处于主导作用。