Chelerythrine chloride binding of guanosine in aqueous solution

In this work, the interaction between chelerythrine (CHE) and guanosine is studied using UV-vis and fluorescence measurements at various temperatures. The UV-vis spectra show that the increasing guanosine concentrations result in the decreasing absorption intensity and red shift of CHE E absorption band (267 nm). The fluorescence spectra are fitted to linear analysis, yielding a binding constant of 1.04×104 L/mol at 298.15 K of CHE with guanosine. Besides, with △rHΘm =-8.26 kJ/mol, △rGmΘ = -22.90 kJ/mol,and △rSmΘ = 49.38 J/(mol K) the interaction should be entropy-driven and exterothermic.     

磁性纳米氧化铁与CdTe量子点相互作用的光谱学研究

采用荧光光谱及紫外-可见吸收光谱研究了不同条件下磁性纳米氧化铁(MION)与CdTe量子点的相互作用, 发现MION对CdTe量子点荧光有猝灭作用. 由Stern-Volmer方程分析得到MION与CdTe量子点结合反应的荧光猝灭速率常数K_q值为7.68×10¹⁵ mol•L^－1•s^－1, 结合紫外-可见吸收光谱进一步证实此过程为静态猝灭过程. 并由Lineweaver-Burk方程得到MION与CdTe量子点结合的热力学焓变(?H^?)值为21.6 kJ•mol^－1、熵变(?S^?)值为210.3 J• mol^－1•K^－1和自由能变(?G^?)值为－41.1 kJ•mol^－1 (298 K). 对其相互作用机理进行探讨, 结果表明MION对CdTe量子点作用为自发过程, 主要存在静电作用.     

牛血清白蛋白与金霉素结合反应的机制研究

以光谱技术与微量热技术相结合的方法研究水溶液中金霉素与牛血清白蛋白分子间结合作用的热力学性质.荧光猝灭法测得该反应的结合常数K=2.09×105L/mol,结合位点数n=1.75,微量法测得反应的焓变△rHm= -17.50 kJ/mol; 依据Forster非辐射能量转移机制,得到授体-受体间的结合距离(r1=1.67 nm, r2=1.46 nm)和能量转移效率(E1=0.41, E2=0.66). 金霉素与牛血清白蛋白分子间有较强的结合作用, 且结合力以疏水作用为主.     

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.     

多光谱法和分子对接模拟法研究黄腐酸与胃蛋白酶的相互作用

利用荧光光谱、 同步荧光光谱、 三维荧光光谱、 紫外-可见吸收光谱、 傅里叶变换红外光谱和圆二色光谱以及分子对接模拟方法研究了黄腐酸(FA)与胃蛋白酶(PEP)之间的相互作用. 荧光光谱分析表明, FA-PEP荧光猝灭的类型为静态猝灭. 根据Stern-Volmer方程和静态猝灭双对数公式计算得到猝灭常数K_sv和结合位点数n. 根据Vant’t Hoff方程计算得到热力学常数ΔH=-59.86 kJ/mol, ΔS=-98.13 J·mol ^-1·K ^-1, ΔG=-30.62 kJ/mol(298 K). 热力学分析表明, 氢键和范德华力是PEP与FA之间的主要结合力, 其反应为自发过程. 根据F?rster非辐射能量转移理论, 计算得到PEP和FA之间的结合距离为2.436 nm, 表明在FA与PEP之间发生了非辐射能量转移. 三维荧光光谱分析表明, 在FA存在下PEP的肽链骨架结构发生了改变. 此外, 紫外-可见吸收光谱、 同步荧光光谱和红外光谱结果表明, FA使PEP的二级构象发生变化. 分子对接模拟结果表明, FA引起PEP荧光猝灭的结合作用力不仅有氢键和范德华力, 还有疏水作用力.     

维生素B_5与牛血清白蛋白相互作用的同步荧光光谱和紫外差光谱研究

采用荧光光谱和紫外差光谱研究了维生素B5与牛血清白蛋白(BSA)的相互作用;计算了3种温度下B5-BSA体系的结合常数和反应的热力学参数.结果表明,B5对牛血清白蛋白的荧光有猝灭作用,猝灭方式为静态猝灭,结合位点数近似为1;B5-BSA体系的ΔH=-63.90kJ.mol-1,ΔG=-35.29kJ.mol-1,ΔS=-96.02J.K-1.mol-1.据此可知,B5与牛血清白蛋白二者间的主要作用力为氢键、范德华力及质子化等.依据Frster非辐射能量转移理论估算出二者之间的结合距离为1.41nm.此外,同步荧光光谱和紫外差光谱分析结果表明,B5可诱导BSA分子构象变化.     

Spectroscopic studies on binding of 1-phenyl-3-(coumarin-6-yl)sulfonylurea to bovine serum albumin

The interaction of 1-phenyl-3-(coumarin-6-yl)sulfonylurea (SU22) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectroscopy combined with UV-absorption, circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy techniques under simulative physiological conditions for the first time. Fluorescence data and UV-absorption spectra revealed that the quenching mechanism of fluorescence of BSA by SU22 was a static quenching process and the number of binding sites was about 0.8858; the thermodynamic parameters (DeltaG=-29.23 kJ mol(-1), DeltaH=-47.48 kJ mol(-1), and DeltaS=-61.24 J mol(-1)K(-1)) explained that hydrogen bond and Van der Waals interaction were the main binding force stabilizing the complex. The binding average distance between SU22 and BSA was obtained (3.20 nm) on the basis of the F?rster's theory. In addition, The CD spectra and FT-IR spectra have proved that BSA secondary structure changed in the presence of SU22 in aqueous solution.     

Studies on the interaction of cinnamic acid with bovine serum albumin

The interaction between cinnamic acid and bovine serum albumin (BSA) have been studied at three temperatures, 296, 303 and 310 K. Fluorescence quenching spectra in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy was used to investigate the drug-binding mode, the binding constant and the protein structure changes in the presence of cinnamic acid in aqueous solution at pH 7.40. The fluorescence quenching constant K(q), K(sv) and the binding constant K were calculated according to Stern-Volmer equation based on the quenching of the fluorescence of BSA in the presence of cinnamic acid. The thermodynamic parameters, the enthalpy (DeltaH) and the entropy change (DeltaS) were estimated to be -16.457 kJ mol(-1) and 38.028 J mol(-1) K(-1) according to the van't Hoff equation. The displacement experiment shows that cinnamic acid can bind to the subdomain IIA (corresponding to Sudlow's drug binding site I). The distance between the tryptophan residues in BSA and cinnamic acid bound to site I was estimated to be 1.63 nm using F?ster's equation on the basis of fluorescence energy transfer. The decreased binding constant in the presence of common ions indicates that common ions have effect on drug-BSA system.     

头孢拉定与血清白蛋白相互作用的光谱学研究

采用荧光和紫外吸收光谱法研究头孢拉定和牛血清白蛋白(BSA)的相互作用.研究发现,头孢柱定荧光猝灭牛血清白蛋白是由于形成了头孢拉定-牛血清白蛋白复合物.分别计算了不同温度下双分子猝灭常数kq和结合常数K.由热力学参数焓变(△H)、熵变(△S)和吉布斯自由能(△G),推断出头孢拉定与BSA的相互作用是一个疏水作用的自发过...     

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.     

Investigation of the interaction between colloidal TiO(2) and bovine hemoglobin using spectral methods

The interaction between bovine hemoglobin (BHb) and TiO(2) colloid was investigated by UV/vis absorption, UV/vis diffuse reflectance spectrum, IR, fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques under physiological pH 7.40. TiO(2) effectively quenched the intrinsic fluorescence of BHb via static quenching. The process of binding TiO(2) on BHb was a spontaneous molecular interaction procedure. The thermodynamic parameters, DeltaH degrees and DeltaS degrees were estimated to be -78.07 kJ mol(-1), -110.93 J mol(-1)K(-1) according to the van' Hoff equation. This indicates that the van der Waals and hydrogen bonds interactions played a major role in stabilizing the TiO(2)-BHb complex. The effect of TiO(2) on the conformation of BHb was analyzed using synchronous fluorescence spectroscopy.     

室温固相反应制备纳米四水磷酸锌的热化学研究

Nanocrystalline zinc phosphate tetrahydrate was synthesized by solid-state reaction at ambient temperature using Na3PO4·12H2O and ZnSO4·7H2O as regents. The enthalpy of reaction and the standard enthalpy of formation of zinc phosphate tetrahydrate were studied by microcalorimeter. According to Hess s law, a new thermochemical cycle was designed. The dissolution enthalpies of reactant (△H1) and product (△H2) were performed by a RD496 microcalorimeter at 298.15 K using aqueous solution of hydrochloric acid (4mol/L) as a calorimetric solvent. Ultraviolet spectrum, conductivity and refractive index were measured respectively. The results show as follows: △H1=(-47.180±0.084) kJ/mol, △H2=(-7.617±0.096 )kJ/mol. The ultraviolet spectra of the above solution are the same. Conductivity values after 500 times diluted are 2180 and 2181μs/cm respectively. Refractive indexes are 1.3679 and 1.3678 respectively. The standard enthalpy value of the reaction was calculated: △rHm=-39.530 kJ/mol. The standard enthalpy of formation for zinc phosphate tetrahydrate are recommended -4354.004 kJ/mol.     

光谱法研究Cu2+与肌红蛋白的相互作用

用紫外吸收光谱、荧光光谱、同步荧光光谱及圆二色(CD)谱研究了Cu2+与肌红蛋白(Mb)的相互作用. 结果发现, Cu2+使Mb的紫外吸收增强, 峰位蓝移, 说明Cu2+与Mb发生了较强的相互作用; Mb的特征荧光峰猝灭, 且随着温度升高猝灭常数Ksv降低, 表明Cu2+对Mb的荧光猝灭机制属于静态猝灭; 计算了不同温度下的结合常数和结合位点数; 由van′t Hoff方程计算出ΔH和ΔS分别为-11.60 kJ/mol和33.77 J·(mol·K)-1, 得出二者之间的作用力主要为静电力; 并依据Förster非辐射能量转移理论确定了给体-受体间的结合距离r=2.56 nm. 同步荧光光谱表明, Cu2+对Mb的构象产生影响, 使色氨酸残基的疏水性下降. CD光谱测得加入Cu2+后, 二级结构发生改变, 使α-螺旋含量降低.     

ADSORPTION OF MACROPOROUS PHOSPHONIC ACID RESIN FOR INDIUM

The adsorption kinetics and mechanism of a nrovel chelate resin, macroporous phosphonic acid resin (PAR) for In(Ill) were investigated Tile statically saturated adsorption capacity is 216mg·g^-1resin at 298K in HAc-NaAc medium. Tire apparent adsorption rate constant is k298=4.84×10^-5 s^-1. Tile adsorption behavior of PAR for In(Ill) obeys the Freundlich isotherm. The thermodynamic adsorption parameters, enthalpy change △H, free energy change △G and entropychange △S of PAR for In(Ⅲ) are 11.5kmol, -12.6kJmol and 80.8Jmol.K, respectively. The apparent activation energy is Ea=3.5k.l/mol. Tire molar coordination ratio of the functional group of PAR to In(Ⅲ) is about 3:1.     

氯化三烷基苄基铵萃取铂(Ⅳ)、钯(Ⅱ)的热力学研究

季铵盐是萃取铂、钯的优良试剂,已广泛应用于铂族元素的分离^[1-3],季铵盐从盐酸体系中萃取铂、钯是按阴离子交换机理进行的^[4-5]。金属配阴离子按阴离子交换机理与有机阳离子生成缔合物。PtCl₆^2-的电荷密度比PdCl₄^2-的小,根据最小电荷密度原理,Pt(Ⅳ)应比Pd(Ⅱ)易被萃取。     

光谱法结合原子力显微镜研究呋喃唑酮与牛血清白蛋白的作用机理

在人体生理(pH=7.4)条件下,应用荧光光谱和紫外光谱法研究药物呋喃唑酮与牛血清白蛋白(BSA)相互作用的机理,确定了呋喃唑酮对BSA的荧光猝灭机制。采用Stern-Volmer方程求出其相互作用的猝灭常数,并由双对数方程求出结合常数Ka和结合位点数n,采用热力学方法判别作用力类型。实验结果指出两者之间相互作用引起的荧光猝灭属静态方式,298K下结合常数Ka为6.50×106 L·mol~(-1),结合位点数n约为1,而作用力类型是氢键和范德华力。另外,还采用红外(IR)光谱、圆二色谱(CD)和原子力显微镜(AFM)研究了呋喃唑酮对BSA构象的影响。     

Synthesis and characterization of polymer eight-coordinate (enH2)[YIII(pdta)(H2O)](2)·10H2O as well as the interaction of [YIII(pdta)(H2O)]2(2-) with BSA

The eight-coordinate (enH2)[YIII(pdta)(H2O)](2)·10H2O (en=ethylenediamine and H4pdta=1,3-propylenediamine-N,N,N',N'-tetraacetic acid) was synthesized, meanwhile its molecular and crystal structures were determined by single-crystal X-ray diffraction technology. The interaction between [Y(III)(pdta)(H2O)]2(2-) and bovine serum albumin (BSA) was investigated by UV-vis and fluorescence spectra. The results indicate that [YIII(pdta)(H2O)]2(2-) quenched effectively the intrinsic fluorescence of BSA via a static quenching process with the binding constant (Ka) of the order of 10(4). Meanwhile, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. Results indicate that the hydrophobic environments around Trp and Tyr residues were all slightly changed. The thermodynamic parameters (ΔG=-25.20 kJ mol(-1), ΔH=-26.57 kJ mol(-1) and ΔS=-4.58 J mol(-1) K(-1)) showed that the reaction was spontaneous and exothermic. What is more, both ΔH and ΔS were negative values indicated that hydrogen bond and Van der Waals forces were the predominant intermolecular forces between [YIII(pdta)(H2O)]2(2-) and BSA.     

Study of the interaction of indirubin with bovine serum albumin

This study examined the interaction of indirubin with bovine serum albumin (BSA) at three temperatures (286, 297, 308 K) at pH 7.40. In the presence of indirubin, the drug-BSA binding mode, binding constant and the protein structure changes in aqueous solution were determined by fluorescence quenching methods including Fourier transform infrared (FT-IR) spectroscopy and UV-Vis spectroscopy. The FT-IR change indicates that indirubin binds to BSA. The change in protein secondary structure accompanying ligand binding has been proved by fluorescence spectra data. The thermodynamic parameters, the enthalpy change (DeltaH), and the entropy change (DeltaS) calculated by the van't Hoff equation possess small negative (-2.744 kJ.mol(-1)) and positive values (112.756 J.mol(-1).K(-1)), respectively, which indicated that hydrophobic interactions play the main role in the binding of indirubin to BSA. Furthermore, the displacement experiment shows that indirubin can bind to the subdomain IIA and the distance between the tryptophan residues in BSA and indirubin bound to site I was estimated to be 2.24 nm according to F?ster's equation on the basis of fluorescence energy transfer.     

Fluorescence studies on the interactions of barbaloin with bovine serum albumin

The fluorescence quenching reactions of barbaloin with bovine serum albumin (BSA) in pH 7.20 Tris-HCl buffer solution were studied. The quenching mechanism of BSA by barbaloin was interpreted using the Stern-Volmer (S-V) mechanism. The binding constant K values were 2.78 x 10(5) (293 K), 1.87 x 10(5) (310 K), 1.25 x 10(5) (318 K), and the number of binding sites (n) were 1.18, 1.14, and 1.09, respectively. In addition, the thermodynamic functions enthalpy (deltaH degrees ) and entropy (deltaS degrees ) for the reaction were also calculated according to Vant's Hoff equation were -23.7 kJ/mol and 23.6 J/mol, respectively. Plausible explanations of the quenching mechanism are discussed on the basis of a hydrophobic interaction between barbaloin and BSA.     

DNA binding studies of a solvatochromic fluorescence probe 3-methoxybenzanthrone

A fluorescence probe of 3-methoxybenzanthrone (MBA) exhibits significant solvatochromic characteristics correlated with the polarity of solvents. The interaction of the solvatochromic fluorescence probe with calf thymus DNA (ct-DNA) has been investigated. In the presence of ct-DNA the fluorescence of MBA is strongly quenched with a blue-shift of emission peak and a hypochromism in absorption spectra. The absorption spectra, fluorescence quenching and fluorescence polarization experiments show that the MBA molecule as an intercalator is inserted into the base-stacking domain of the ct-DNA double helix, and the interaction of the nucleobases with the MBA molecule causes quenching of fluorescence and hypochromism in the absorption spectra. The intrinsic binding constant and the binding site number were determined to be 1.70 x 10(5) mol l-1 in base pairs and six, respectively. The I0/I versus [ct-DNA] plot shows linear relationship in the range covering 4.3 x 10(-7)-1.02 x 10(-4) mol l-1 in base pairs which can be used for ct-DNA determination. The limit of detection was found to be 4.3 x 10(-7) mol l-1 in base pairs (0.5 microgram ml-1).