咖啡因与氧氟沙星的相互作用

利用紫外光谱、一阶导数紫外光谱及荧光光谱研究了咖啡因与氧氟沙星的相互作用,结果发现,咖啡因通过与氧氟沙星杂环共轭体系的堆积形成配合物引起氧氟沙星溶液荧光猝灭,二者形成1∶1的配合物,结合反应的表观结合常数分别为KA(T=299K)=1.18×104L.mol-1;KA(T=309K)=0.84×104L.mol-1,二者之间存在着范德华力以及杂环共轭体系的堆积效应。     

酸度对氧氟沙星与牛血清白蛋白结合的影响

牛血清白蛋白在不同pH的溶液中存在N（pH ～7.0）,B（pH ～9.0）和E（pH 3.5以下）等几种同分异构形态。 采用紫外-可见光谱和荧光光谱研究了酸度对牛血清白蛋白（BSA）的结构以及对不同结构的BSA和氧氟沙星的相互作用的影响,应用荧光猝灭现象和Frster理论,求出了4个不同pH下两者结合的猝灭常数、 能量转移效率和结合距离等参数。结果显示,氧氟沙星与牛血清白蛋白在pH 4.9时结合常数最大（1.928 1×105 L·mol-1）,结合距离小（r=2.55 nm）,猝灭效应最好（8.63×104 L·mol-1）;氧氟沙星与牛血清白蛋白的结合过程中,静态猝灭和非辐射能量转移是导致牛血清白蛋白荧光猝灭的原因;中性、 弱酸和弱碱性环境对两者的结合没有太大的影响,静电作用不是两者相互作用的主要作用力。使用同步荧光技术考察了氧氟沙星对BSA构象的影响。     

铜(Ⅱ)配合物与DNA作用的光谱法研究

采用紫外光谱和荧光光谱研究了配离子[Cu(A)₂]2＋(其中A=邻菲络啉(phen),联吡啶(bpy),乙二胺(en))与小牛胸腺DNA的相互作用。实验发现配合物的存在使DNA碱变性的pH增大,变性后增色效应减小。EB-DNA体系的荧光强度随[Cu(phen)₂]2＋的加入迅速减弱。在DNA存在下,配离子被猝灭剂[Fe(CN)₆]4-的发光猝灭程度减小。进一步研究了配体分子平面的大小对配合物与DNA作用的影响。结果表明,铜配合物与DNA之间发生了插入作用,且该作用随配体芳环平面的减小而减弱, 即[Cu(phen)₂]2＋＞[Cu(bpy)₂]2＋＞[Cu(en)₂]2＋。     

环丙沙星、氧氟沙星同时与牛血清白蛋白分子作用的荧光光谱

在pH=7.40的水溶液中,环丙沙星(CPFX)、氧氟沙星(OFLX)能够猝灭牛血清白蛋白(BSA)的荧光。当两种药物共存时BSA荧光被进一步猝灭。据此建立了利用荧光发光光谱法进行喹诺酮类药物CPFX与OFLX间相互作用的研究。结果表明:药物间存在相互作用,使药物与蛋白间的结合常数减小、结合稳定性下降,游离型药物含量增加,造成药效增强;药物对蛋白荧光的猝灭属于静态猝灭,药物与蛋白结合位点数约为1。根据Frster非辐射能量转移理论,确定了药物与蛋白之间的结合距离r7nm,属于非辐射能量转移。药物间的相互作用使r值增加,结合距离增大。同步荧光光谱研究表明药物间的相互作用对蛋白构象产生影响,使蛋白质分子伸展,疏水性降低。     

DNA介导复合膜中[Ru(bpy)3]2+与Cu(Ⅱ)间光诱导电子转移

由于DNA与[Ru(bpy)₃]2+(bpy=2,2′-联吡啶)及Cu2+间的静电作用,用自铸膜法在铟锡氧化物(ITO)上制备了橙红色[Ru(bpy)₃]2+-DNA-Cu2+复合膜,并应用稳态和暂态荧光光谱、紫外可见光谱、荧光显微镜和扫描电镜对复合膜进行了表征和DNA介导的光诱导电子转移(PET)研究。结果表明,[Ru(bpy)₃]2+-DNA-Cu2+复合膜(摩尔比为10∶20∶1)呈现了明显的吸收特征峰(450 nm)和发射峰(λ_em=595 nm),发光呈单指数衰减,发光寿命为188.6 ns,Cu2+通过DNA介导PET机制猝灭[Ru(bpy)₃]2+发光,猝灭常数为6.94×103 L·mol-1,猝灭速率常数为3.80×1010 L·mol-1·s-1;复合膜中Cu2+摩尔比(10倍)的增大使发射峰蓝移了11 nm,吸收和发射强度衰减至消失,Cu2+通过静态猝灭机制削弱[Ru(bpy)₃]2+发光。此外,对比于溶液和复合膜中Cu2+对[Ru(bpy)₂(tatp)]2+-DNA(tatp=1,4,8,9-四氮三苯)的发光调控,Cu2+仅能因静电作用猝灭复合膜中[Ru(bpy)₃]2+的发光。     

荧光光谱法研究萘酚绿B与牛血清白蛋白相互作用特征

在不同温度下,研究了萘酚绿B(NGB)作用于牛血清白蛋白的荧光猝灭光谱、同步荧光光谱、三维荧光光谱和紫外-可见吸收光谱特征。分别用Stern-Volmer方程和Lineweaver-Burk双倒数方程等处理实验数据,证实了在试验浓度和温度范围内,NGB与BSA可相互作用形成复合物, 荧光猝灭作用符合静态猝灭作用特征,作用力主要是疏水作用力和静电作用力;得到了相互作用的相关参数K_LB,ΔHθ,ΔGθ和ΔSθ等的平均值分别为1.411×105 L·mol-1,-5.707 kJ·mol-1,-30.25 kJ·mol-1和79.95 J·K-1,结合位点数为1.258,为研究NGB对蛋白质构象的影响和在生物体内的生物学效应等提供了重要信息。     

7-羟基黄酮及磷酰化7-羟基黄酮与DNA的弱相互作用荧光法研究

以溴化乙锭(EB)为荧光探针,研究了7-羟基黄酮及磷酰化7-羟基黄酮与DNA的弱相互作用。实验结果表明,两种化合物与DNA间均存在弱相互作用,但与7-羟基黄酮相比,磷酰化7-羟基黄酮对DNA更具亲和力。随着温度的升高,7-羟基黄酮及磷酰化7-羟基黄酮对DNA-EB体系的荧光猝灭常数降低,两种化合物均可与DNA形成复合物,此猝灭过程为静态猝灭。根据Stern-Volmer方程和Scatchard方程,常温下7-羟基黄酮及磷酰化7-羟基黄酮对DNA-EB体系的荧光猝灭常数和它们与DNA的固有的结合常数分别为：K_q1=601 L·mol-1,K_q2=1 381 L·mol-1;K₁=2.07×104 L ·mol-1,K₂=3.19×104 L·mol-1。     

光谱法研究柔红霉素衍生物DNR-D3与DNA相互作用

在人体生理条件下(pH7.4),利用紫外光谱法和荧光光谱法研究了本实验室合成的柔红霉素衍生物DNR-D3与小牛胸腺DNA(ctDNA)的相互作用。实验发现,在ctDNA存在下DNR-D3的紫外吸收光谱发生减色效应且出现红移现象,这表明DNR-D3与ctDNA相互作用的结合方式以嵌插为主。通过20,30,37℃条件下ctDNA与DNR-D3相互作用的荧光光谱,判断ctDNA与DNR-D3之间荧光猝灭方式为静态猝灭。利用荧光数据计算不同温度下的结合常数,结合位点数及热力学参数,从而判断DNR-D3与ctDNA的作用方式以嵌插为主,作用力类型是以氢键和静电作用为主,此过程是放热的焓熵协同驱动过程。DNR-D3的荧光猝灭50%时DNR-D3与ctDNA的摩尔浓度比Rc=7/25,这表明DNR-D3的蒽环与ctDNA发生了强烈的嵌插作用,DNR-D3显示出了较强的抗癌活性。通过研究可知,DNR-D3有望成为抗癌活性候选药物。     

染料木素铬(Ⅲ)配合物与DNA相互作用的研究

在pH 7.2 Tris缓冲溶液中,采用紫外、DNA熔点、荧光、粘度等手段研究了染料木素铬(Ⅲ)配合物与小牛胸腺DNA(ctDNA)的作用机制,探讨了其作用模式。当加入一定量的ctDNA时,染料木素铬(Ⅲ)配合物的紫外吸收光谱的最大吸收峰产生明显的减色效应;而配合物体系的荧光强度、共振光散射信号随ctDNA的加入逐渐增强。配合物的存在能有效猝灭EB-DNA体系的荧光,且猝灭方式为静态猝灭。同时ctDNA的熔点和ctDNA溶液的粘度随配合物的加入而增大。据此推断,染料木素铬(Ⅲ)配合物与ctDNA之间具有较强的作用,配合物主要以插入方式与DNA结合,二者的键合常数为1.9×105 L·mol-1。该研究结果提示染料木素铬(Ⅲ)配合物有望作为抗癌活性候选药物,值得进一步深入研究。     

防己诺林碱与牛血清白蛋白相互作用的研究

在不同温度下,用荧光猝灭光谱、同步荧光光谱和紫外-可见吸收光谱,研究了防己诺林碱与BSA相互作用的光谱学行为。防己诺林碱对BSA有较强的荧光猝灭作用。根据不同温度下防己诺林碱对BSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,表明防己诺林碱对BSA的荧光猝灭作用属于静态猝灭。根据Frster非辐射能量转移理论计算出了防己诺林碱与BSA间的结合距离R(27 ℃ 2.51 nm; 37 ℃ 2.72 nm; 47℃ 2.89 nm)、结合常数K_A(27 ℃ 1.05×105 L·mol-1; 37 ℃ 3.31×105 L·mol-1; 47 ℃ 7.24×105 L·mol-1)及对应温度下的热力学参数。热力学数据表明二者主要靠疏水作用力结合,同时用同步荧光光谱探讨了防己诺林碱对BSA构象的影响。     

荧光探针法研究百草枯与DNA的相互作用

以中性红（NR）为分子探针,应用紫外光谱法和荧光光谱法研究了除草剂百草枯（PQ）与小牛胸腺DNA（ctDNA）之间的相互作用。在pH7.3的Tris-HCl（5×10-2mol.L-1）缓冲溶液中,NR分子主要以嵌插方式结合到ctDNA双螺旋结构上,百草枯的加入抑制了NR与ctDNA之间的结合,用Stern-Volmer方程进行数据处理,表明百草枯对ctDNA-NR的荧光猝灭不是单纯的静态或动态猝灭方式,属于混合型的。综合紫外光谱、离子强度等研究证实,在该实验条件下,百草枯与DNA之间存在静电和嵌插两种作用。     

Interaction Between Methylene Blue and CalfThymus Deoxyribonucleic Acid by Spectroscopic Technologies

Characterization of the interaction between methylene blue (MB) and calf thymus deoxyribonucleic acid (ctDNA) was investigated by UV absorption spectra, fluorescence spectra, fluorescence polarization and fluorescence quenching experiments by ferrocyanide. The above results indicated that the binding modes of MB to ctDNA were relative to the molar ratio γ (γ=[DNA]/[MB]). At low γ ratios (γ < 4), remarkable hypochromic effect with no shift of λ_max in the absorption spectra of MB was observed in the presence of increasing amounts of ctDNA, the fluorescence of MB was efficiently quenched by the ctDNA bases and the fluorescence polarization of MB was slightly increased, which indicated that MB cations bound to phosphate groups of ctDNA by electrostatic interaction and then stacked on the surface of ctDNA helix. While at high γ ratios (γ > 6), besides the fluorescence of MB was quenched efficiently by the ctDNA bases, a red shift (about 3 nm) in the absorption spectra of MB was observed and the fluorescence polarization of MB was obviously increased, which indicated the intercalation binding that MB molecules were intercalated into the space of two neighbouring DNA base pairs was the preferred mode. Effects of K₄Fe(CN)₆ on the fluorescence quenching of the MB-ctDNA system at low and high γ ratios were also performed. The results showed that at γ = 1.7, the quenching effect by ferrocyanide was higher than that of pure MB, while at γ = 13.6 a decreased quenching of the fluorescence intensity was observed as compared with that of pure MB, which further proved the above conclusion. In addition, the mechanisms of the hypochromic effect and the fluorescence quenching were also discussed in detail.     

Specific binding of a dihydropyrimidinone derivative with DNA: Spectroscopic,calorimetric and modeling investigations

One of the dihydropyrimidinone derivative 5-(ethoxycarbonyl)-6-methyl-4-(4-methoxyphenyl)-3,4-dihydropyrimidin-2(1H)-one (EMMD) was synthesized, and its binding properties with calf-thymus DNA (ctDNA) were investigated using spectroscopic, viscometric, isothermal titration calorimetric (ITC) and molecular modeling techniques. Fluorescence spectra suggested that the fluorescence enhancement of the binding interaction of EMMD to ctDNA was a static process with ground state complex formation. The binding constant determined with spectroscopic titration and ITC was found to be in the same order of 10⁴ M^?1. According to the results of the viscosity analysis, fluorescence competitive binding experiment, fluorescence quenching studies, absorption spectral and ITC investigations, it can be concluded that EMMD is intercalative binding to ctDNA. Furthermore, the results of molecular modeling confirmed those obtained from spectroscopic, viscosimetric and ITC investigations. Additionally, ITC studies also indicated that the binding interaction is predominantly enthalpy driven.     

Study on the toxic interactions of Ni with DNA using neutral red dye as a fluorescence probe

The interaction between Ni²⁺ and calf thymus DNA (ctDNA) was investigated in simulated physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as CD spectra. The experimental results showed that the conformational changes in DNA helix induced by Ni²⁺ are the reason for the fluorescence quenching of the DNA-NR system. From the experimental results, conclusion can be drawn that Ni²⁺ can cause structural changes of ctDNA and bind with DNA by electrostatic interaction. At the same time, the paper proved that conformation changes of DNA can also lead to the fluorescence decrease of DNA-probe systems.     

染料木素酯化修饰物与ctDNA的相互作用

在pH7.2的Tris-HCl缓冲溶液中,采用紫外光谱和荧光光谱法研究了2种新型染料木素酯化修饰物,染料木素7-乙酰阿魏酸酯(GenA)和染料木素7,4′-二-乙酰阿魏酸酯(GenDA)与小牛胸腺DNA(ctDNA)的相互作用。随着ctDNA的加入,GenA与GenDA的紫外吸收和荧光光谱的强度均发生不同程度的降低。ctDNA对化合物的荧光猝灭为静态猝灭过程。在293K时化合物与ctDNA的结合常数分别为2.81×106L.mol-1和1.19×104L.mol-1。同时通过I-离子效应、离子强度、DNA熔点、粘度法等研究证实,在该实验条件下,GenA与ctDNA之间具有较强的作用,主要以嵌插方式结合;GenDA主要以沟槽方式与ctDNA作用。     

Study on the Interaction of an Anthracycline Disaccharide with DNA by Spectroscopic Techniques and Molecular Modeling

This study was designed to examine the interaction of 4'-O-(a-L-Cladinosyl) daunorubicin (DNR-D5), a disaccharide anthracycline with calf thymus deoxyribonucleic acid (ctDNA) by UV/Vis in combination with fluorescence spectroscopy and molecular modeling techniques under physiological conditions (Britton-Robinson buffer solutions, pH?=?7.4). By the analysis of UV/Vis spectrum, it was observed that upon binding to ctDNA the anthraquinone chromophore of DNR-D5 could slide into the base pairs. Moreover, the large binding constant indicated DNR-D5 had a high affinity with ctDNA. At the same time, fluorescence spectra suggested that the quenching mechanism of the interaction of DNR-D5 to ctDNA was a static quenching type. The binding constants between DNR-D5 and ctDNA were calculated based on fluorescence quenching data at different temperatures. The negative ?G implied that the binding process was spontaneous, and negative ?H and negative ΔS suggested that hydrogen bonding force most likely played a major role in the binding of DNR-D5 to ctDNA. Moreover, the results obtained from molecular docking corroborate the experimental results obtained from spectroscopic investigations.     

染料木素及其葡萄糖苷与DNA相互作用的研究

在pH 7.2 Tris缓冲溶液中,采用紫外、荧光、粘度等方法研究了染料木素、染料木素葡萄糖苷、染料木素7,4’-二-O-β-D-葡萄糖苷与小牛胸腺ctDNA的作用。结果表明,在ctDNA存在下,染料木素及其葡萄糖苷的紫外吸收光谱的最大吸收峰均产生明显的减色效应。三种化合物的加入均能有效猝灭EB-DNA体系的荧光,而猝灭方式并不唯一。另外,ctDNA溶液的粘度也都随三种化合物的加入而增大。据此推断,染料木素及其葡萄糖苷与ctDNA之间具有较强的作用,可能以部分插入及氢键作用与ctDNA结合,其作用强弱顺序为染料木素葡萄糖苷>染料木素7,4’-二-O-β-D-葡萄糖苷>染料木素。结果提示染料木素的7位或4’位葡萄糖基化修饰有望作为抗癌活性候选物,值得进一步深入研究。     

Research on the interaction of cr(III) complex of genistein with DNA

The interaction of the Cr(III) complex of genistein (GEN-Cr) with calf thymus DNA (ctDNA) in Tris (pH 7.2) buffer was investigated using UV spectra, DNA melting, fluorescence spectra and viscosity. From the absorption titration experiment, no obvious red shift was found, but the notable hypochromicities were observed. When C(DNA)/C(GEN-Cr) = 3, the pi-pi* transitions of the complex at 272 nm showed a decrease in intensity of 29.1%, which indicated that there was remarkable intercalation between complex and DNA base pairs, involving a strong pi-stacking interacting between them. The binding constant for the complex was K = 1.9 x 10(5) mol x L(-1). From the melting curves of ctDNA in the absence and presence of the complex, the melting temperature of ctDNA was found to increase by 5.5 degrees C from 74 to 79.5 degrees C, owing to the increased stability of the helix in the presence of the complex that was intercalated into the double helix. The complex could emit weak luminescence in Tris buffer. The emission intensity of the complex at 340 nm increased steadily with the addition of ctDNA. The result suggested that the complex got into a hydrophobic environment inside the DNA and avoided the effect of solvent water molecules. The strong interaction of the complex and ctDNA also resulted in greatly enhanced intensity of the resonance light scattering spectra. The emission intensity of DNA-EB system at 600 nm decreased remarkably with increasing the complex concentration, which indicated that the complex could be intercalated into DNA and replace EB from the DNA-EB system. According to the classical Stern-Volmer equation, the quenching plots at 25 and 37 degrees C both appeared approximately linear. These results showed that there was one predominant quenching style in this process. Viscosity experiments were carried out by an Ubbelodhe viscometer at 20.0 (+/- 0.1) degrees C. The relative viscosity of ctDNA increased steadily with the increased in the complex. The result clearly showed that the complex could be intercalated between DNA base pairs, causing an extension of the helix, and thus increased the viscosity of DNA. The results above indicated that there is a relatively strong interaction between the GEN-Cr complex and ctDNA, and the complex could bind ctDNA mainly by intercalation. The research suggested that the GEN-Cr complex may be a promising candidate for anticancer, which deserves further research.     

共振光散射法研究甲萘威与DNA的作用及其应用

通过共振光散射光谱(RLS)和电子吸收光谱的特征,探求了甲萘威与ctDNA的结合方式,实验表明在pH 1.97的条件下,甲萘威与ctDNA既有表面聚集又有嵌入式结合的双重作用,结合形式与二者之间的浓度比有关。在此条件下,甲萘威与ctDNA作用的RLS强度与ctDNA的浓度呈线性关系,据此建立了一种简单快速测定ctDNA的新方法。ctDNA的浓度在0.02～3 μg·mL-1的范围内与RLS强度呈良好的线性关系,线性方程为I= 200.77c(μg·mL-1)+118.91,相关系数r=0.998 9。该方法已成功地用于人工混合样品的测定。