Resonance Rayleigh scattering study of the interaction of bleomycinA_5 with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in batho- chromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum condi- tions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Resonance Rayleigh scattering study of the interaction of bleomycinA<Subscript>5</Subscript> with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in bathochromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum conditions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Fluorescence Quenching and Binding Interaction of l0-Methylacridinium Iodide to Nucleic Acids

Interaction of 10‐methylacridinium iodide (MAI) as fluorescence probe with nucleobases, nucleosides and nucleic acids has been studied by UV‐visible absorption and fluorescence spectroscopy. It was found that fluorescence of MAI is strongly quenched by the nucleobases, nucleosides and nucleic acids, respectively. The quenching follows the Stern‐Volmer linear equation. The fluorescence quenching rate constant (k_q) was measured to be 10^9‐10¹⁰ (L/mol)/s within the range of diffusion‐controlled rate limit, indicating that the interaction between MAI and nucleic acid and their precursors is characteristic of electron transfer mechanism. In addition, the binding interaction model of MAI to calf thymus DNA (ct‐DNA) was further investigated. Apparent hypochromism in the absorption spectra of MAI was observed when MAI binds to ct‐DNA. Three spectroscopic methods, which include (1) UV spectroscopy, (2) fluorescence quenching of MAI, (3) competitive dual‐probe method of MAI and ethidium bromide (EB), were utilized to determine the affinity binding constants (K) of MAI and ct‐DNA. The binding constants K obtained from the above methods gave consistent data in the same range (1.0–5.5) × 10⁴L/mol, which lend credibility to these measurements. The binding site number was determined to be 1.9. The influence of thermal denaturation and phosphate concentration on the binding was examined. The binding model of MAI to ct‐DNA including intercalation and outside binding was investigated.     

Binding of nucleosides with the cytotoxic plant alkaloid sanguinarine: Spectroscopic and thermodynamic studies

In spite of a large number of studies of the interaction of the cytotoxic plant alkaloid sanguinarine(SAN) with nucleic acids,the anticancer mechanism of SAN is still not clear.In contrast to the large number of studies of the interaction mechanism of SAN with DNA,there have been relatively few studies of the interaction of SAN with nucleosides.In this work,the interaction of SAN with three nucleosides-thymidine(T),uridine(U),and adenosine(A)-was investigated using a combination of conventional fluorescence and UV-vis spectroscopic techniques;thermodynamic calculations were also carried out at physiological pH 7.2.The binding processes of SAN with the different nucleosides were characterized by hypochromic and bathochromic effects in the absorption spectra of SAN and by the quenching of the fluorescence intensity of SAN.The measurements of fluorescence lifetime,the variations of the absorption spectra of the fluorophore,and the dependence of the quenching on the temperature indicated that the fluorescence quenching is static.The Stern-Volmer plot is nonlinear and approximately quadratic showing that,in this process,one SAN molecule can bind with two nucleoside molecules.These studies,together with our earlier studies of the binding of SAN with cytidine(C) and guanosine(G),showed that the binding constants of SAN with the five nucleosides at T = 308.15,318.15,and 328.15 K decreased in the order C > G > T > U > A and at T = 298.15 K decreased in the order G > C > T > U > A,and that the binding of SAN with the various nucleosides is not only slightly exothermic but also entropy-driven.All these results together with fluorescence quenching experiments advance good evidence concerning the interaction of SAN with various nucleosides.Such studies of the interaction mechanism of alkaloids with DNA may promote the development of new drugs.     

Spectroscopic Study of the Interaction between New Fluorescent Dyes with Nucleic Acids

Considerableefforthasbeencofltinuingtofocusonthedevelopmentofnewfluorescentdyestorecognizenucleicacids'-'.Althoughdansylisawell-knownsensitivehydrophobicprobewhichhasbeenwidelyutilizedasafluorescentprobeforthestudyofproteins,yetlittleefforthasbeenfocusedontheexploringdansylamidederivativeswhichmayhavespecificeffectsonnucleicacids.Sincethebindingaffinityofsuchfluorophorestopolynucleotideswasgreatlyaffectedbytheirsidechainsubstitutions,inthisworkseveralnewdansylderivativeswithspecificbindingtonu…     

Chlorobenzylidine-herring sperm DNA interaction: binding mode and thermodynamic studies

The interaction of chlorobenzylidine with herring sperm DNA has been investigated by fluorescence, absorption, DNA melting experiment and differential scanning calorimetry (DSC). When bound to DNA, chlorobenzylidine shows hypochromism and red shift in absorption spectra, fluorescence quenching and polarization increasing in fluorescence spectra and increasing in DNA melting temperature. These spectral characteristics strongly support intercalation of chlorobenzylidine into herring sperm DNA. Scatchard plots constructed from fluorescence titration data give a binding constant of 3.2 x 10(4) M(-1) and a binding site size of six base pairs per bound drug molecule. The intercalative interaction is exothermic with a van't Hoff enthalpy of -30.6 kJ mol(-1). This result is obtained from DSC experiment. In addition, DeltaG degrees =-28.5 kJ mol(-1), and DeltaS degrees =-7.1 J mol(-1) K(-1). These results show that the binding of chlorobenzylidine to herring sperm DNA is exothermic.     

光谱法研究Ge-132与DNA的作用机理

利用吸收光谱、DNA碱变性曲线、荧光光谱研究了Ge-132与DNA的相互作用。在Ge-132存在下,DNA的紫外吸收光谱产生明显的减色效应。同时,Ge-132的存在使DNA碱变性的pH值增大,变性后增色效应减小,实验结果表明,Ge-132主要是以嵌入方式与DNA结合的。     

Study on the interaction of morphine chloride with deoxyribonucleic acid by fluorescence method

The mode and mechanism of the interaction of morphine chloride, an important alkaloid compound to calf thymus deoxyribonucleic acid (ct DNA) was investigated from absorption and fluorescence titration techniques. Hypochromic effect was founded in the absorption spectra of morphine when concentration of DNA increased. The decreased fluorescence study revealed non-cooperative binding of the morphine to DNA with an affinity of 3.94x10(3)M(-1), and the stoichiometry of binding was characterized to be about one morphine molecule per nucleotide. Stern-Volmer plots at different temperatures proved that the quenching mechanism was static. Ferrocyanide quenching study showed that the magnitude of K(SV) of the bound morphine was lower than that of the free one. In addition, it was found that ionic strength could affect the binding of morphine and DNA. Fluorescence polarization and denatured DNA studies also applied strong evidences that morphine molecule was partially intercalated between every alternate base pairs of ct DNA. As observed from above experiments, intercalation was well supported as the binding mode of morphine and ct DNA.     

Quadracyclic Adenine: A Non‐Perturbing Fluorescent Adenine Analogue

Fluorescent‐base analogues (FBAs) comprise a group of increasingly important molecules for the investigation of nucleic acid structure and dynamics as well as of interactions between nucleic acids and other molecules. Here, we report on the synthesis, detailed spectroscopic characterisation and base‐pairing properties of a new environment‐sensitive fluorescent adenine analogue, quadracyclic adenine (qA). After developing an efficient route of synthesis for the phosphoramidite of qA it was incorporated into DNA in high yield by using standard solid‐phase synthesis procedures. In DNA qA serves as an adenine analogue that preserves the B‐form and, in contrast to most currently available FBAs, maintains or even increases the stability of the duplex. We demonstrate that, unlike fluorescent adenine analogues, such as the most commonly used one, 2‐aminopurine, and the recently developed triazole adenine, qA shows highly specific base‐pairing with thymine. Moreover, qA has an absorption band outside the absorption of the natural nucleobases (>300 nm) and can thus be selectively excited. Upon excitation the qA monomer displays a fluorescence quantum yield of 6.8 % with an emission maximum at 456 nm. More importantly, upon incorporation into DNA the fluorescence of qA is significantly less quenched than most FBAs. This results in quantum yields that in some sequences reach values that are up to fourfold higher than maximum values reported for 2‐aminopurine. To facilitate future utilisation of qA in biochemical and biophysical studies we investigated its fluorescence properties in greater detail and resolved its absorption band outside the DNA absorption region into distinct transition dipole moments. In conclusion, the unique combination of properties of qA make it a promising alternative to current fluorescent adenine analogues for future detailed studies of nucleic acid‐containing systems.     

Study on the phosphorescence characterizations of palmatine chloride on the solid substrate and its interaction with ctDNA

The spectroscopic characterizations of solid substrate room temperature phosphorescence (SS-RTP) of palmatine (Pal) have been studied. Strong RTP signal at 615 nm can be induced on filter paper in the presence of TIAc. The interaction between calf thymus DNA (ctDNA) and Pal has been investigated at pH 6.90 using fluorescence, UV-vis, SS-RTP and cyclic voltammogram spectroscopy. Strong binding affinity of Pal with DNA is revealed from the absorption and fluorescence studies in the liquid state. With the addition of ctDNA, the fluorescence intensity of Pal is enhanced greatly and UV-vis spectra show no apparent hypochromicity and red shift, which indicates that Pal intercalates into ctDNA bases. However, this conclusion could not explain the phenomena from fluorescence polarization and denatured DNA measurements, which indicate that groove binding is at least the main binding mode. Binding constant and binding site size have been calculated to be 2.57 × 10⁴ L/mol and 0.16 based on Scatchard plot from fluorescence titration data. Groove binding has also been supported by phosphorescence lifetime and anion quenching experiments. Above studies demonstrate that there should exist intercalative binding and groove binding in the interaction of Pal and DNA. Furthermore, cyclic voltammogram study suggests that electrostatic binding exists at the same time exactly. Taken together, the binding model obtained in this study is mixed-mode.     

Quadracyclic adenine: a non-perturbing fluorescent adenine analogue

Fluorescent-base analogues (FBAs) comprise a group of increasingly important molecules for the investigation of nucleic acid structure and dynamics as well as of interactions between nucleic acids and other molecules. Here, we report on the synthesis, detailed spectroscopic characterisation and base-pairing properties of a new environment-sensitive fluorescent adenine analogue, quadracyclic adenine (qA). After developing an efficient route of synthesis for the phosphoramidite of qA it was incorporated into DNA in high yield by using standard solid-phase synthesis procedures. In DNA qA serves as an adenine analogue that preserves the B-form and, in contrast to most currently available FBAs, maintains or even increases the stability of the duplex. We demonstrate that, unlike fluorescent adenine analogues, such as the most commonly used one, 2-aminopurine, and the recently developed triazole adenine, qA shows highly specific base-pairing with thymine. Moreover, qA has an absorption band outside the absorption of the natural nucleobases (>300?nm) and can thus be selectively excited. Upon excitation the qA monomer displays a fluorescence quantum yield of 6.8?% with an emission maximum at 456?nm. More importantly, upon incorporation into DNA the fluorescence of qA is significantly less quenched than most FBAs. This results in quantum yields that in some sequences reach values that are up to fourfold higher than maximum values reported for 2-aminopurine. To facilitate future utilisation of qA in biochemical and biophysical studies we investigated its fluorescence properties in greater detail and resolved its absorption band outside the DNA absorption region into distinct transition dipole moments. In conclusion, the unique combination of properties of qA make it a promising alternative to current fluorescent adenine analogues for future detailed studies of nucleic acid-containing systems.     

A temperature-dependent interaction of neutral red with calf thymus DNA

Neutral red (NR) is used as a probe to study the temperature and concentration dependent interaction of a cationic dye with nucleic acid. A temperature-dependent interaction of NR with calf thymus DNA (CT DNA) has been studied by differential pulse voltammetry (DPV), UV-Visible absorption, circular dichroism (CD) and fluorescence spectroscopy. The experimental results of increasing peak current, changes in the UV-Visible absorption and fluorescence spectra of NR and decreasing the induced circular dichroism (ICD) intensity show that (i) the binding mode of NR molecules is changed from intercalating into DNA base pairs to aggregating along the DNA double helix and (ii) the orientation of NR chromophore in DNA double helix is also changed with the temperature.     

2-羟基苯乙酮铜(Ⅱ)配合物与ct-DNA的键合作用研究

以小牛胸腺DNA为靶点,通过紫外可见吸收光谱、稳态荧光发射光谱、圆二色谱和DNA粘度滴定实验,从分子水平研究了2-羟基苯乙酮铜(Ⅱ)配合物[ Cu(HAP)2] (1)与ct-DNA的键合方式.结果表明:配合物[ Cu(HAP)2] (1)主要通过插入作用和静电结合方式与ct-DNA形成键合作用,推测插入作用应基于2-...     

Absorption,Fluorescence and Resonance Rayleigh Scattering Spectra of Interaction of Papain with Calf Thymus DNA

In weak acidic medium, interaction between papain and calf thymus DNA (ctDNA) resulted in absorption spectral change, fluorescence quenching of papain and remarkable enhancement of resonance Rayleigh scattering (RRS). The interaction types and binding modes were discussed by characteristics of RRS, absorption, fluorescence and circular dichroism spectra combining thermodynamic data. Four interaction types include electrostatic attraction, hydrophobic force, hydrogen bonding and aromatic stacking interaction. Papain interacted with the major groove of ctDNA. Aromatic stacking interaction is the main reason of change of absorption spectrum and fluorescence quenching of papain. Surface enhanced scattering effect, resonance energy transfer effect, increase of molecular volume and conformational change make contribution to RRS enhancement. The enhanced RRS intensity (ΔI) is directly proportional to the concentration of ctDNA or papain. The detection limit (3σ) is 5.2 ng·mL^?1 for ctDNA and 5.6 ng·mL^?1 for papain. This creates conditions for determination of papain and ctDNA.     

藻蓝蛋白对Au(Ⅲ)原位还原与纳米Au(0)形成动态过程的谱学研究

在4℃、避光条件下,将藻蓝蛋白(PC)与AuCl₃作用,通过UV、FS、FT-IR等谱学方法研究了PC与Au(Ⅲ)作用的动态过程,结果显示:PC在615nm的特征吸收峰强度明显减弱,并随Au(Ⅲ)浓度增加和时间延长单调降低;PC的荧光发射峰和荧光激发峰也均呈现衰减趋势.同时通过TEM观察到纳米Au(0)粒子形成,纳米金基本呈球形,有较窄的分布尺寸,粒径在20 nm左右,均匀地分散于PC中,这是PC原位还原Au(Ⅲ)所形成的.     

硫酸长春碱与牛血清白蛋白相互作用的研究

本文利用荧光光谱法和紫外吸收光谱法研究了硫酸长春碱（Vinblastine Sulfate,VS）与牛血清白蛋白（Bovine Serum Albumin,BSA）的相互作用,讨论了药物与蛋白相互作用时药物对蛋白微环境的影响。求得不同温度下（298K、308K和318K）药物与蛋白相互作用的结合常数及结合位点数。利用F6rster能量转移理论得药物与蛋白间的键合距离为3.34nm。热力学参数（△H=14.34kJ／mol,△S=36.92J／（mol&#183;K））表明维持药物与蛋白质的相互作用力主要是疏水作用和静电作用。此外,基于硫酸长春碱的荧光猝灭效应,探讨了药物-蛋白质体系的几种物理化学参数包括电荷密度、离解常数及量子产率的变化效应;以及共存离子对药物-蛋白质体系结合常数的影响。     

Spectroscopic Characterization of Thiazole Orange-3 DNA Interaction

The interaction of a new derivative of thiazole orange (TO-3) with calf thymus DNA (ctDNA) has been investigated by fluorescence and absorption spectroscopy. When TO-3 binds to ctDNA, absorption bands exhibit significant hypochromicity at low base pair/dye ratio (BP/D ratio), and high BP/D show hyperchromicity with red shift. The spectral changes are attributed to the different species formed between TO-3 and ctDNA in the titration course of the dye molecule with DNA. Multivariate curve resolutions–alternating least squares (MCR–ALS) is applied to the absorption measurements recorded to recover the concentration profiles and the pure spectra of the DNA/TO-3 complexes involved in the process. The binding constant and size of the binding site have been determined spectrophotometrically using the McGhee von Hippel equation. MCR–ALS has been used to reveal the precise concentration profiles of all detectable species formed between ctDNA and TO-3 and their pure spectral profiles.     

Spectroscopic studies on the interaction of pazufloxacin with calf thymus DNA

Fluorescence spectra, absorption spectra, DNA viscosity titrations, competition experiment, and iodide quenching experiment were used to study the interaction of DNA with pazufloxacin. DNA quenches the fluorescence of pazufloxacin significantly. No red shift and isobestic points are observed in UV titration experiment. DNA viscosity and iodide quenching results suggest that pazufloxacin does not intercalate into DNA. SsDNA has a stronger quenching effect on pazufloxacin than dsDNA has. Pazufloxacin interacts with DNA in a different mode from ethidium bromide, which is a typical intercalator of DNA. All these results indicate that pazufloxacin interacts with calf thymus DNA in the mode of groove binding. The quenching constant and thermodynamic constants have also been determined.     

一种用于细胞核成像的新型双光子荧光探针

本文报道了具有大双光子活性吸收截面的DNA探针BMVEC, 同时首次利用双光子显微镜完成了与DAPI的复染实验, 实验结果证实了BMVEC对细胞核的选择性标记能力.     

米托蒽醌与生物大分子DNA结合平衡的研究

米托蒽醌(MX)是一个广谱高效的葸醌类抗癌新药(下式),核酸是该类药物的主要细胞作用靶位,它通过与DNA结合,影响DNA的转译和复制,从而起到抗癌作用。研究这类药物与核酸的作用对于阐明抗癌机理具有重要意义,为此,广泛地开展了这方面的研究。