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1.
The interaction of La3+ to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by La3+ was a static quenching process and the binding constant is 1.75×104 L mol−1 and the number of binding sites is 1 at 289 K. The thermodynamic parameters (ΔH=−20.055 kJ mol−1, ΔG=−23.474 kJ mol−1, and ΔS=11.831 J mol−1 K−1) indicate that electrostatic effect between the protein and the La3+ is the main binding force. In addition, UV-vis, CD, and synchronous fluorescence results showed that the addition of La3+ changed the conformation of BSA.  相似文献   

2.
Peng Ju 《Journal of luminescence》2011,131(8):1724-1730
The interaction between flower-like CdSe nanostructure particles (CdSe NP) and bovine serum albumin (BSA) was investigated from a spectroscopic angle under simulative physiological conditions. Under pH 7.4, CdSe NP could effectively quench the intrinsic fluorescence of BSA via static quenching. The binding constant (KA) was 6.38, 3.27, and 1.90×104 M−1 at 298, 304, and 310 K, respectively and the number of binding sites was 1.20. According to the Van't Hoff equation, the thermodynamic parameters (ΔH°=−77.48 kJ mol−1, ΔS°=−168.17 J mol−1 K−1) indicated that hydrogen bonds and van der Waals forces played a major role in stabilizing the BSA−CdSe complex. Besides, UV-vis and circular dichroism (CD) results showed that the addition of CdSe NP changed the secondary structure of BSA and led to a decrease in α-helix. These results suggested that BSA underwent substantial conformational changes induced by flower-like CdSe nanostructure particles.  相似文献   

3.
The water-soluble Pr (Ⅲ) and Nd (Ⅲ) complexes with an ofloxacin derivative have been prepared and characterized. The single-crystal X-ray diffraction showed that the Pr (III) and Nd (III) complexes have the similar molecular structure. Under physiological pH condition, the effects of [PrL(NO3)2(CH3OH)](NO3) and [NdL(NO3)2(CH3OH)](NO3) on bovine serum albumin (BSA) were examined using fluorescence spectroscopy in combination with UV-vis absorbance and circular dichroism (CD) spectra. The result reveals that the quenching mechanism of fluorescence of BSA by two complexes is a static quenching process and the number of binding sites is about 1 for both. The thermodynamic parameters (ΔH=−14.52 kJ mol−1, ΔS=56.54 J mol−1 K−1 for [PrL(NO3)2(CH3OH)](NO3) and ΔH=−24.63 kJ mol−1, ΔS=22.07 J mol−1 K−1 for [NdL(NO3)2(CH3OH)](NO3)) indicate that hydrophobic and electrostatic interactions are the main binding force in the complexes-BSA system. The binding average distance between complexes and BSA was obtained on the basis of Förster's theory. In addition, it was proved by the CD spectra that the BSA secondary structure was changed in the presence of complexes in an aqueous solution.  相似文献   

4.
The interaction between the antimicrobial drug sulfamethazine (STM) and bovine serum albumin (BSA) has been studied using steady state and synchronous fluorescence spectroscopy. Fluorescence emission data revealed that BSA (2×10−6 M) fluorescence was statically quenched by STM at various concentrations, which implies that STM-BSA complex has been formed. The fluorescence emission data was analyzed via applying the Stern-Volmer analysis in combination with thermodynamic investigation, where obtained results revealed that quenching is static with quenching constants of 2.371, 1.658, and 0.916×105 M−1 at 298, 304, and 310 K, respectively. Binding constants and number of binding sites at different temperatures were also determined by applying the Scatchard method, which in turn were used to construct the van't Hoff plot in order to estimate the enthalpy (ΔH) and entropy changes (ΔS) for the complexation process. An average of 1.00±0.17 was estimated for the number of sites of BSA, which indicated that STM binds to BSA with stoichiometric ratio of 1:1. The values that were estimated from the van't Hoff plot for ΔH and (ΔS) were −36.8 kJ mol−1 and −14.9 J mol−1 K−1, respectively, which indicate that the STM-BSA complex is stabilized with hydrogen bonds and van der Waals interactions. Synchronous fluorescence data was obtained at Δλ of 15 and 60 nm, where obtained results confirmed that STM binds to BSA at the tryptophan residue (Trp. 213). In addition, the distance between STM and the Trp. 213 was estimated via employing the Förster's non-radiative energy-transfer theory, and was found to be 2.73 nm, which in turn indicated that STM can bind to BSA with high probability.  相似文献   

5.
The interaction of disperse blue SBL (DBSBL) with bovine serum albumin (BSA) was investigated using fluorescence, UV-visible and far-UV circular dichroism (CD) spectroscopy. The results showed that the fluorescence of BSA was quenched by DBSBL through static quenching after correcting for the inner filter effects (IFE). The binding constant Kb of DBSBL with BSA at 288, 298 and 303 K were 0.116×106, 3.18×106 and 12.3×106 L mol−1, respectively. The thermodynamic parameters, standard enthalpy change (ΔH0) and standard entropy change (ΔS0), for the reaction were evaluated to be 227.2 kJ mol−1 and 886 J mol−1 K−1 according to the van’t Hoff equation. The above data suggested that the forces acting between DBSBL and BSA were predominantly hydrophobic interactions. The results of UV-visible absorption and far-UV CD spectroscopy also revealed that the conformation and microenvironment of BSA molecule were changed after DBSBL binding to BSA. At 288 K one binding site was present but at higher temperatures a second binding site was detected between DBSBL and the BSA molecule. The lower bound for the distance between the bound dye and the Trp residue is 2.35 nm as calculated from Forster energy transfer.  相似文献   

6.
In this paper, the interaction between barbital and bovine serum albumin (BSA) was investigated by the method of fluorescence spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by barbital was the result of the formation of BSA-barbital complex, and the effective quenching constants (Ka) were 1.468×104, 1.445×104 and 1.403×104 M−1 at 297, 303 and 310 K, respectively. The thermodynamic parameters enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be −2.679 kJ mol−1 and 70.76 J mol−1 K−1, respectively, according to the van’t Hoff equation. The results indicated that hydrophobic and electrostatic interactions were the dominant intermolecular force in stabilizing the complex. The results of synchronous fluorescence spectra showed that binding of barbital with BSA can induce conformational changes in BSA. In addition, the effects of Cu2+ and Zn2+ on the constants of BSA-barbital complex were also discussed.  相似文献   

7.
Naringenin, a flavanone compound highly enriched in grapefruits, has been identified as a possible inhibitor of cell proliferation; and thus has the potential to act as an antitumorigenic agent. In this study, the binding of naringenin to bovine serum albumin (BSA) was studied at the physiological conditions (pH=7.40) by fluorescence and UV-vis spectroscopy. Naringenin strongly quenches the intrinsic fluorescence of BSA, and a decrease in the fluorescence quenching constant was observed together with an increase in temperature, which indicates that the fluorescence quenching of BSA by naringenin is a result of the formation of naringenin-BSA complex. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that naringenin bind to BSA with the binding affinities of the order 104 L mol−1. Thermodynamic parameters such as ΔG, ΔH and ΔS, were calculated at different temperatures, showing that electrostatic interactions were mostly responsible for the binding of naringenin to BSA. Site marker competitive displacement experiments demonstrating that naringenin bind with high affinity to site I (subdomain IIA) of BSA. Furthermore, the effect of metal ions to naringenin-BSA system was studied, and the specific binding distance r (3.30 nm) between donor (Trp-212) and acceptor (naringenin) was obtained according to fluorescence resonance energy transfer (FRET).  相似文献   

8.
The interaction between promethazine hydrochloride (PMT) and bovine serum albumin (BSA) in vitro was investigated by means of fluorescence spectroscopy and absorption spectroscopy. The fluorescence of BSA was quenched remarkably by PMT and the quenching mechanism was considered as static quenching by forming a complex. The association constants Ka and the number of binding sites n were calculated at different temperatures. The BSA-PMT binding distance was determined to be less than 8 nm, suggesting that energy transfer from BSA to PMT may occur. The thermodynamic parameters of the interaction between PMT and BSA were measured according to the van’t Hoff equation. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be −23.62 kJ mol−1 and −0.10 J mol−1 K−1, respectively, which indicated that the interaction of PMT with BSA was driven mainly by van der Waals forces and hydrogen bonds. The binding process was a spontaneous process in which Gibbs free energy change (ΔG) was negative. In addition, the results of synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that binding of PMT with BSA can induce conformational changes in BSA.  相似文献   

9.
The binding properties of diprophylline (DPP) to lysozyme (Lys) were investigated using fluorescence spectroscopy in combination with UV-vis absorption techniques under simulative physiological conditions. Results of fluorescence measurement indicated that the intrinsic fluorescence of Lys was strongly quenched by DPP. The binding constants and the number of binding sites at different temperatures (298, 310, and 318 K) calculated with the data obtained from fluorescence quenching experiments via the modified Stern-Volmer equation were 8.61×104 L mol−1 and 1.34; 10.36×104 L mol−1 and 1.22; 12.85×104 L mol−1 and 1.11, respectively. Positive values of ΔH0 and ΔS0 obtained according to the Van’t Hoff equation for the formation of the DPP-Lys complex implied that typical hydrophobic interactions might play a significant role during the binding process. Furthermore, the effect of DPP on the conformation change of Lys was analyzed using synchronous fluorescence measurement. The effects of common co-ions on the interaction of DPP with Lys were also discussed.  相似文献   

10.
The interaction between lomefloxacin (LMF) and human lactoferrin (Hlf) was studied by using fluorescence, circular dichroism (CD) spectroscopic and molecular modeling measurements. By the fluorescence quenching results, it was found that the binding constant KA=8.69×105 L mol−1, and number of binding sites n=1.75 at physiological condition. Experimental results observed showed that the binding of LMF to Hlf induced conformational changes of Hlf. The participation of tyrosyl and tryptophanyl residues of protein was also estimated in the drug-Hlf complex by synchronous fluorescence. The quantitative analysis data of far-UV CD spectra from that of the α-helix 37.4% in free Hlf to 30.2% in the LMF-Hlf complex further confirmed that secondary structure of the protein was changed by LMF. Near-UV CD showed perturbations around tryptophan and tyrosine residues which involves perturbations of tertiary structure. The thermodynamic parameters like, ΔH° and ΔS°, have been calculated to be 63.411 kJ mol−1 and 231.104 J mol−1 K−1, respectively. Thermodynamic analysis showed that hydrophobic interactions were the main force in the binding site but the hydrogen bonding and electrostatic interaction could not be excluded which in agreement with the result of molecular docking study. The distance r between donor and acceptor was obtained according to fluorescence resonance energy transfer (FRET) and found to be 1.78 nm. The interaction between LMF and Hlf has been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer. Furthermore, the study of molecular modeling that LMF could bind to the α-helixes between Pro145-Asn152 and Phe167-Gln172 regions and hydrophobic interaction was the major acting force for the binding site, which was in agreement with the thermodynamic analysis.  相似文献   

11.
The interactions of bovine serum albumin (BSA) with two local anesthetics, procaine hydrochloride (PCH) and tetracaine hydrochloride (TCH) were studied using spectroscopic methods such as fluorescence and ultraviolet visible (UV-vis), and electrochemical techniques including cyclic voltammetry (CV) and differential pulsed stripping voltammetry (DPSV). The results obtained from these techniques turned out that both PCH and TCH could bind to BSA. The binding constants (KA) and the number of binding sites (n) of the two drugs with BSA at different temperatures were determined, respectively. At 291 K, KA was found as 2.40×104 and 1.42×104 L mol−1 and n was 1.03 and 0.99 for PCH-BSA and TCH-BSA, respectively. According to van’t Hoff equation, the thermodynamic parameters, ΔG, ΔH and ΔS, were obtained, showing the involvement of hydrophobic and electrostatic force in these interactions. Based on the theory of the Förster energy transference, the distance between the acceptor (PCH or TCH) and the donor (BSA) were determined as 2.32 and 3.62 nm for PCH and TCH, respectively. The effects of Fe3+, Cu2+, Mg2+, Mn2+, Zn2+ and Ca2+ on the binding of PCH or TCH to BSA were also evaluated.  相似文献   

12.
M. Ghali 《Journal of luminescence》2010,130(7):1254-20848
The author reports on a strong fluorescence quenching of a model transport protein, bovine serum albumin BSA, when bioconjugated with CdS quantum dots QDs. The 4.4 nm size CdS QDs were synthesized using wet chemistry method and were characterized using UV-vis spectroscopy, scanning electron microscopy SEM and X-ray diffraction XRD techniques. It was found that the BSA fluorescence quenching increases linearly with increasing the CdS QDs concentrations in the range of 3×10−7-2.0×10−6 mol L−1. This quenching is explained in terms of Stern-Volmer equation and is ascribed to static quenching with quenching constant 1.321×104 L mol−1 at 300 K.  相似文献   

13.
The interactions of mitomycin C (MMC), fluorouracil (FU), mercaptopurine (MP) and doxorubicin hydrochloride (DXR) with bovine serum albumin (BSA) were studied by spectroscopic method. Quenching of fluorescence of serum albumin by these drugs was found to be a static quenching process. The binding constants (KA) were 9.66×103, 2.08×103, 8.20×102 and 7.50×103 L mol−1 for MMC-, FU-, MP- and DXR-BSA, respectively, at pH 7.4 Britton-Robinson buffer at 28 °C. The thermodynamic functions such as enthalpy change (ΔH), entropy change (ΔS) and Gibbs free-energy change (ΔG) for the reactions were also calculated according to the thermodynamic equations. The main forces in the interactions of these drugs with BSA were evaluated. It was found that the interactions of MMC and FU with BSA were exothermic processes and those of MP and DXR with BSA were endothermic. In addition, the binding sites on BSA for the four drugs were probed by the changes of binding properties of these drugs with BSA in the presence of two important site markers such as ibuprofen and indomethacin. Based on the Föster theory of non-radiation energy transfer, the binding distances between the drugs and tryptophane were calculated and they were 3.00, 1.14, 2.85, and 2.79 nm for MMC, FU, MP and DXR, respectively.  相似文献   

14.
Titanium dioxide (TiO2) nanoparticles (NPs) are widely used as an important kind of biomaterials. The interaction between TiO2 (P25) at 20 nm in diameter and human serum albumin (HSA) was studied by fluorescence spectroscopy in this work. Under the simulative physiological conditions, fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants (Ka) were 2.18±0.04×104, 0.87±0.05×104, 0.68±0.06×104 M−1 at 298, 304 and 310 K, respectively. In addition, according to the Van’t Hoff equation, the thermodynamic functions standard enthalpy (ΔH0) and standard entropy (ΔS0) for the reaction were calculated to be −75.18±0.15 kJ mol−1 and −170.11±0.38 J mol−1 K−1. These results indicated that TiO2 NPs bond to HSA mainly by van der Waals force and hydrogen bonding formation in low dielectric media, and the electrostatic interactions cannot be excluded. Furthermore, the effects of common ions on the binding constant of TiO2 NPs-HSA complex were discussed.  相似文献   

15.
Heat capacities of the electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its radical-ion salt NH4-TCNQ have been measured at temperatures in the 12-350 K range by adiabatic calorimetry. A λ-type heat capacity anomaly arising from a spin-Peierls (SP) transition was found at 301.3 K in NH4-TCNQ. The enthalpy and entropy of transition are ΔtrsH=(667±7) J mol−1 and ΔtrsS=(2.19±0.02) J K−1 mol−1, respectively. The SP transition is characterized by a cooperative coupling between the spin and the phonon systems. By assuming a uniform one-dimensional antiferromagnetic (AF) Heisenberg chains consisting of quantum spin (S=1/2) in the high-temperature phase and an alternating AF nonuniform chains in the low-temperature phase, we estimated the magnetic contribution to the entropy as ΔtrsSmag=0.61 J K−1 mol−1 and the lattice contribution as ΔtrsSlat=1.58 J K−1 mol−1. Although the total magnetic entropy expected for the present compound is R ln 2 (=5.76 J K−1 mol−1), a majority of the magnetic entropy (∼4.6 J K−1 mol−1) persists in the high-temperature phase as a short-range-order effect. The present thermodynamic investigation quantitatively revealed the roles played by the spin and the phonon at the SP transition. Standard thermodynamic functions of both compounds have also been determined.  相似文献   

16.
The interaction of methyl blue (MB) with human serum albumin (HSA) was studied by fluorescence and absorption spectroscopy. The intrinsic fluorescence of HSA was quenched by MB, which was rationalized in terms of the static quenching mechanism. The number of binding sites and the apparent binding constants at different temperatures were obtained from the Stern-Volmer analysis of the fluorescence quenching data. The thermodynamic parameters determined by the van’t Hoff analysis of the binding constants (ΔH°=39.8 kJ mol−1 and ΔS°=239 J mol−1 K−1) clearly indicate that binding is absolutely entropy-driven and enthalpically disfavored The efficiency of energy transfer and the distance between the donor (HSA) and the acceptor (MB) were calculated as 60% and 2.06 nm from the Förster theory of non-radiation energy transfer.  相似文献   

17.
The fluorescence and ultraviolet spectroscopies were explored to study the interaction between edaravone (EDA) and bovine serum albumin (BSA) under imitated physiological condition. The experimental results show that the fluorescence quenching mechanism between EDA and BSA is a combined quenching (dynamic and static quenching). The binding constants, binding sites, and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. According to Förster non-radiation energy transfer theory, the binding distance between EDA and BSA was calculated to be 3.10 nm. The effect of EDA on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effects of some common metal ions Mg2+, Ca2+, Cu2+, and Ni2+ on the binding constant between EDA and BSA were examined.  相似文献   

18.
The binding of nobiletin to human serum albumin (HSA) was investigated by fluorescence, UV-vis, FT-IR, CD, and molecular modeling. Fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants (K) at four different temperatures (289, 296, 303 and 310 K) were 4.054, 4.769, 5.646 and 7.044×104 M−1, respectively. The enthalpy change (ΔH0) and the entropy changes (ΔS0) were calculated to be 1.938 kJ mol−1 and 155.195 J mol−1 K−1 according to the Van’t Hoff equation. The binding average distance, r, between the donor (HSA) and the acceptor (nobiletin) was evaluated and found to be 2.33 nm according to the Förster's theory of non-radiation energy transfer. Changes in the CD and FT-IR spectra were observed upon ligand binding along with a significant degree of tryptophan fluorescence quenching on complex formation. Computational mapping of the possible binding sites of nobiletin revealed the molecule to be bound in the large hydrophobic cavity of subdomain IIA.  相似文献   

19.
Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-FER results in hydrogen bonding of the adsorbed N2 molecules with the zeolite Si(OH)Al Brønsted acid groups. This hydrogen bonding interaction leads to activation, in the IR, of the fundamental NN stretching mode, which appears at 2331 cm−1. From the infrared spectra taken over a temperature range, while simultaneously recording integrated IR absorbance, temperature and nitrogen equilibrium pressure, the thermodynamics of the adsorption process was studied. The standard adsorption enthalpy and entropy resulted to be ΔH° = −20(±1) kJ mol−1 and ΔS° = −131(±10) J mol−1 K−1, respectively.  相似文献   

20.
Adsorption of carbon dioxide on a faujasite-type H-Y zeolite (Si:Al = 2.6:1) was studied by variable-temperature (200-290 K range) infrared spectroscopy. Adsorbed CO2 molecules interact with the Brønsted acid Si(OH)Al groups located inside the zeolite supercage, bringing about a characteristic bathochromic shift of the O-H stretching mode from 3645 cm−1 (free OH group) to 3540 cm−1 (hydrogen-bonded CO2 adsorption complex). Simultaneously, the asymmetric (ν3) mode of adsorbed CO2 is observed at 2353 cm−1. From the observed variation of the integrated intensity of the 3645 and 2353 cm−1 IR absorption bands upon changing temperature, corresponding values of standard adsorption enthalpy and entropy were found to be ΔH° = −28.5(±1) kJ mol−1 and ΔS° = −129(±10) J mol−1 K−1. Comparison with the reported values of ΔH° for CO2 adsorption on other zeolites is briefly discussed.  相似文献   

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