The irreversible conformational transition of bovine serum albumin (BSA) from α-helix to β-sheet, induced by electric field near the electrode surface, was monitored by circular dichroism (CD) with a long optical pa...The irreversible conformational transition of bovine serum albumin (BSA) from α-helix to β-sheet, induced by electric field near the electrode surface, was monitored by circular dichroism (CD) with a long optical path thin layer cell (LOPTLC).展开更多
The interaction of raltitrexed（RTX） with bovine serum albumin（BSA） was investigated by steady state/lifetime fluorescence spectroscopy and circular dichroism（CD） spectroscopy under the simulative physiological c...The interaction of raltitrexed（RTX） with bovine serum albumin（BSA） was investigated by steady state/lifetime fluorescence spectroscopy and circular dichroism（CD） spectroscopy under the simulative physiological conditions.The results of fluorescence titration reveal that RTX could strongly quench the intrinsic fluorescence of BSA via a static quenching procedure.The obtained binding constant K A of RTX with BSA was 478630 and 44259 L/mol at 298 and 310 K,respectively.According to van＇t Hoff equation,the thermodynamic parameters ΔH,ΔG and ΔS were calculated,indicating that hydrophobic forces were the predominant intermolecular forces in stabilizing the complex.The binding process was a spontaneous process,in which Gibbs free energy change was negative.According to F rster＇s non-radioactive energy transfer theory,the distance r between donor（BSA） and acceptor（RTX） was 3.82 nm,suggesting that the energy transfer from BSA to RTX occurred with high probability.Displacement experiment and the number of binding sites calculation confirmed that RTX could bind to the site-I of BSA.Furthermore,the effects of pH and some metal ions on the interaction of RTX with BSA were also investigated.The results of synchronous fluorescence and CD spectra show that the RTX-BSA binding induced conformational changes in BSA.展开更多
The interactions of bovine serum albumin (BSA) with two alkylimidazolium-based ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), ...The interactions of bovine serum albumin (BSA) with two alkylimidazolium-based ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), in buffer solutions at pH 7.0 were investigated by isothermal titration calorimetry (ITC) and circular dichroism (CD). CD spectra showed that the two ionic liquids changed the secondary structure of BSA. Data process was based on the supposition that there were several independent types of binding sites on each BSA molecule for the two ligand molecules. The results obtained by using this supposition combined with Langmuir adsorption model showed that there were two types of such binding sites. One was the high affinity binding site, and the other was the low affinity binding site. The binding constants, changes in enthalpy, entropy and Gibbs free energy for the two types of binding were obtained, which showed that the two types of binding were driven by a favorable entropy increase. Furthermore, for either the ionic liquids, the number of the high affinity binding sites is much smaller than that of the low affinity ones. These results were interpreted with the molecular structure of BSA and the different substituent groups on imidazole ring of the two ionic liquid molecules.展开更多
Fluorescence spectroscopy, Fourier transform infrared （FT-IR） spectroscopy, circular dichroism （CD） and FT-Raman spectroscopy were employed to analyze the binding of the asiatic acid （AA） to bovine serum albumin...Fluorescence spectroscopy, Fourier transform infrared （FT-IR） spectroscopy, circular dichroism （CD） and FT-Raman spectroscopy were employed to analyze the binding of the asiatic acid （AA） to bovine serum albumin （BSA） under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by AA was the result of the formation of BSA-AA complex. The fluorescence quenching mechanism of BSA by AA was a static quenching procedure. According to the Van＇t Hoff equation, the thermodynamic parameters enthalpy change （△H0） and entropy change （△S0） for the reaction were evaluated to be --12.55 kJ·mol^-1 and 67.08 kJomol 1, respectively, indicating that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The influence of AA on the conformation of BSA has also been analyzed on the basis of FT-IR, CD and FT-Raman spectra.展开更多
The binding of kaempferol-3,7-α-L-rhamnopyranoside （KRR） with bovine serum albumin （BSA） was investi- gated by different spectroscopic methods under simulative physiological conditions. Analysis of fluorescence q...The binding of kaempferol-3,7-α-L-rhamnopyranoside （KRR） with bovine serum albumin （BSA） was investi- gated by different spectroscopic methods under simulative physiological conditions. Analysis of fluorescence quenching data of BSA by KRR at different temperatures using Stern-Volmer methods revealed the formation of a ground state KRR-BSA complex with moderate binding constant of the order 10^4 Lomol-1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van＇t Hoff enthalpy （△H0） and entropy （△S0） of the interaction were estimated to be --26.53 kJ.mol-1 and 3.33 J.mol-l.K-1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA-KRR complex. According to the F6ster theory of non-radiation energy transfer, the distance r between the donor （BSA） and the acceptor （KRR） was obtained （r= 2.83 nm）. Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV-Vis absorption and circular dichroism （CD） results indicated that the KRR binding could cause conformational changes of BSA.展开更多
The interactions of amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and their derivatives with bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. Ex-perimental r...The interactions of amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and their derivatives with bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. Ex-perimental results showed that the fluorescence intensity of BSA decreased after the addition of different modified den-drimers, and the extent of the fluorescence quenching caused by various modified dendrimers strongly depends upon the different functional groups on their surfaces. We also inves-tigated the influence of pH and ionic strength on the interac-tion between various modified dendrimers and BSA. Circu-lar dichroism (CD) spectroscopic measurements showed that the content of α-helix structure of BSA decreased after the addition of different modified dendrimers, which indicated that dendrimers induced changes in the secondary structure of BSA.展开更多
在模拟生理条件下,用荧光光谱法结合圆二色谱法研究了吲哚美辛(IM)与牛血清白蛋白(BSA)的相互作用。实验结果表明,IM对BSA的猝灭机制属于形成复合物的静态猝灭过程,由修正的Stern-Volmer方程求出不同温度下相应的结合常数分别为11.87...在模拟生理条件下,用荧光光谱法结合圆二色谱法研究了吲哚美辛(IM)与牛血清白蛋白(BSA)的相互作用。实验结果表明,IM对BSA的猝灭机制属于形成复合物的静态猝灭过程,由修正的Stern-Volmer方程求出不同温度下相应的结合常数分别为11.87×104、8.351×104、6.110×104 L.mol-1。利用范特霍夫方程及结合常数的数据分别计算体系的焓变、熵变和吉布斯自由能变。焓变值(-42.54 kJ.mol-1)和熵变值(-45.65J.mol-1.K-1)表明,氢键和van der Waals是IM与BSA之间缔合作用的主要作用力。圆二色谱、三维荧光光谱的研究结果显示,在与IM结合后,BSA中α-螺旋的含量减少,说明在与IM结合反应过程中,BSA的微环境和构型发生了改变。展开更多
文摘The irreversible conformational transition of bovine serum albumin (BSA) from α-helix to β-sheet, induced by electric field near the electrode surface, was monitored by circular dichroism (CD) with a long optical path thin layer cell (LOPTLC).
基金Supported by the National Natural Science Foundation of China(No.30973659)
文摘The interaction of raltitrexed（RTX） with bovine serum albumin（BSA） was investigated by steady state/lifetime fluorescence spectroscopy and circular dichroism（CD） spectroscopy under the simulative physiological conditions.The results of fluorescence titration reveal that RTX could strongly quench the intrinsic fluorescence of BSA via a static quenching procedure.The obtained binding constant K A of RTX with BSA was 478630 and 44259 L/mol at 298 and 310 K,respectively.According to van＇t Hoff equation,the thermodynamic parameters ΔH,ΔG and ΔS were calculated,indicating that hydrophobic forces were the predominant intermolecular forces in stabilizing the complex.The binding process was a spontaneous process,in which Gibbs free energy change was negative.According to F rster＇s non-radioactive energy transfer theory,the distance r between donor（BSA） and acceptor（RTX） was 3.82 nm,suggesting that the energy transfer from BSA to RTX occurred with high probability.Displacement experiment and the number of binding sites calculation confirmed that RTX could bind to the site-I of BSA.Furthermore,the effects of pH and some metal ions on the interaction of RTX with BSA were also investigated.The results of synchronous fluorescence and CD spectra show that the RTX-BSA binding induced conformational changes in BSA.
文摘The interactions of bovine serum albumin (BSA) with two alkylimidazolium-based ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), in buffer solutions at pH 7.0 were investigated by isothermal titration calorimetry (ITC) and circular dichroism (CD). CD spectra showed that the two ionic liquids changed the secondary structure of BSA. Data process was based on the supposition that there were several independent types of binding sites on each BSA molecule for the two ligand molecules. The results obtained by using this supposition combined with Langmuir adsorption model showed that there were two types of such binding sites. One was the high affinity binding site, and the other was the low affinity binding site. The binding constants, changes in enthalpy, entropy and Gibbs free energy for the two types of binding were obtained, which showed that the two types of binding were driven by a favorable entropy increase. Furthermore, for either the ionic liquids, the number of the high affinity binding sites is much smaller than that of the low affinity ones. These results were interpreted with the molecular structure of BSA and the different substituent groups on imidazole ring of the two ionic liquid molecules.
基金Project supported by the National Natural Science Foundation of China （Nos. 20671023, 30460153, 21061002）, the Key Project of Chinese Ministry of Education （Nos. 03101, 204111）, Guangxi Natural Science Foundation of China （No. 2010GXNSFF013001）, and the Innovation Project of Guangxi Graduate Education （No. 2009106020703M42）.
文摘Fluorescence spectroscopy, Fourier transform infrared （FT-IR） spectroscopy, circular dichroism （CD） and FT-Raman spectroscopy were employed to analyze the binding of the asiatic acid （AA） to bovine serum albumin （BSA） under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by AA was the result of the formation of BSA-AA complex. The fluorescence quenching mechanism of BSA by AA was a static quenching procedure. According to the Van＇t Hoff equation, the thermodynamic parameters enthalpy change （△H0） and entropy change （△S0） for the reaction were evaluated to be --12.55 kJ·mol^-1 and 67.08 kJomol 1, respectively, indicating that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The influence of AA on the conformation of BSA has also been analyzed on the basis of FT-IR, CD and FT-Raman spectra.
基金This work was supported by National Natural Science Foundation of China （Nos. 21061002, 20861002）, Guangxi Natural Science Foundation of China （Nos. 2010GXNSFF013001, 2011GXNSFC018009）.
文摘The binding of kaempferol-3,7-α-L-rhamnopyranoside （KRR） with bovine serum albumin （BSA） was investi- gated by different spectroscopic methods under simulative physiological conditions. Analysis of fluorescence quenching data of BSA by KRR at different temperatures using Stern-Volmer methods revealed the formation of a ground state KRR-BSA complex with moderate binding constant of the order 10^4 Lomol-1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van＇t Hoff enthalpy （△H0） and entropy （△S0） of the interaction were estimated to be --26.53 kJ.mol-1 and 3.33 J.mol-l.K-1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA-KRR complex. According to the F6ster theory of non-radiation energy transfer, the distance r between the donor （BSA） and the acceptor （KRR） was obtained （r= 2.83 nm）. Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV-Vis absorption and circular dichroism （CD） results indicated that the KRR binding could cause conformational changes of BSA.
基金supported by the National Natural Science Foundation of China(Grant No.30370405).
文摘The interactions of amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and their derivatives with bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. Ex-perimental results showed that the fluorescence intensity of BSA decreased after the addition of different modified den-drimers, and the extent of the fluorescence quenching caused by various modified dendrimers strongly depends upon the different functional groups on their surfaces. We also inves-tigated the influence of pH and ionic strength on the interac-tion between various modified dendrimers and BSA. Circu-lar dichroism (CD) spectroscopic measurements showed that the content of α-helix structure of BSA decreased after the addition of different modified dendrimers, which indicated that dendrimers induced changes in the secondary structure of BSA.
文摘在模拟生理条件下,用荧光光谱法结合圆二色谱法研究了吲哚美辛(IM)与牛血清白蛋白(BSA)的相互作用。实验结果表明,IM对BSA的猝灭机制属于形成复合物的静态猝灭过程,由修正的Stern-Volmer方程求出不同温度下相应的结合常数分别为11.87×104、8.351×104、6.110×104 L.mol-1。利用范特霍夫方程及结合常数的数据分别计算体系的焓变、熵变和吉布斯自由能变。焓变值(-42.54 kJ.mol-1)和熵变值(-45.65J.mol-1.K-1)表明,氢键和van der Waals是IM与BSA之间缔合作用的主要作用力。圆二色谱、三维荧光光谱的研究结果显示,在与IM结合后,BSA中α-螺旋的含量减少,说明在与IM结合反应过程中,BSA的微环境和构型发生了改变。
