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1.
The interaction between a classic uncoupler (2,4-dinitrophenol, DNP) and bovine serum albumin (BSA) was investigated by fluorescence
spectroscopy under the physiological conditions. The fluorescence quenching constants were calculated by the Stern-Volmer
equation, and based upon the temperature dependence of quenching constants, it was proved that DNP caused a static quenching
of the intrinsic fluorescence of BSA. Owing to the static quenching mechanism, different associative binding constants at
various temperatures were determined and thus the thermodynamic parameters, namely enthalpy (ΔH = −21.12 kJ mol−1) and entropy changes (ΔS = 23.51 J mol−1 K−1) could be calculated based on the binding constants. Moreover, the enthalpy and entropy changes are consistent with the “Enthalpy-Entropy
Compensation” equation obtained from our previous work. The negative enthalpy and positive entropy indicated that the electrostatic
interactions played a major role in DNP-BSA binding process. Site marker competitive displacement experiments were carried
out by using fluorescence and isothermal titration calorimetry (ITC) methods. These results showed that DNP bound with high
affinity to Sudlow’s site I (subdomain IIA) of BSA. The distance (r = 3.78 nm) between donor (BSA) and acceptor (DNP) was obtained according to the mechanism of fluorescence resonance energy
transfer (FRET). Furthermore, the results of synchronous fluorescence and circular dichroism (CD) spectroscopic studies indicated
that the microenvironment and the secondary conformation of BSA were altered. The above results were supported by theoretical
molecular modeling methods. 相似文献
2.
The binding of quercetin to lysozyme (LYSO) in aqueous solution was investigated by fluorescence spectroscopy, UV-vis absorption
spectroscopy and molecular simulation at pH 7.4. The fluorescence quenching of LYSO by addition of quercetin is due to static
quenching, the binding constants, K
a
, were 3.63 × 104, 3.31 × 104 and 2.85 × 104 L·mol−1 at 288, 298 and 308 K, respectively. The thermodynamic parameters, enthalpy change, ∆H, and entropy change, ∆S, were noted to be −7.56 kJ·mol−1 and 61.07 J·mol−1·K−1. The results indicated that hydrophobic interaction may play a major role in the binding process. The distance r between the donor (LYSO) and acceptor (quercetin) was determined as 3.34 nm by the fluorescence resonance energy transfer.
The synchronous fluorescence spectroscopy showed the polarity around the tryptophan residues increased and the hydrophobicity
decreased. Furthermore, the study of molecular simulation indicated that quercetin could bind to the active site (a pocket
made up of 24 amino-acid residues) of LYSO mainly via hydrophobic interactions and that there were hydrogen interactions between
the residues (Gln 57, Ile 98) of LYSO and quercetin. The accessible surface area (ASA) calculation verified the important
roles of tryptophan (Trp) residues during the binding process. 相似文献
3.
In this paper, several spectroscopic techniques were used to investigate the interaction of engeletin (ELN) with bovine serum
albumin (BSA). The analysis of UV–Vis absorption and fluorescence spectra revealed that ELN and BSA formed a static complex
ELN–BSA, and ELN quenched the fluorescence of BSA effectively. According to the thermodynamic parameters ΔS
0 = 47.27 J·mol−1·K−1 and ΔΗ
0 = −10.34 kJ·mol−1, the hydrophobic and hydrogen bond interactions were suggested to be the major interaction forces between ELN and BSA. Raman
spectroscopy indicated that the binding of ELN slightly changed the conformations and microenviroment of BSA and decreased
the α–helix content of BSA. 相似文献
4.
Zhuming Wang Xijuan Tan Donghua Chen Qiaoli Yue Zhenghua Song 《Journal of fluorescence》2009,19(5):801-808
It was first found that the intrinsic fluorescence of lysozyme at 340 nm can be quenched by cephalosporin analogues through
the static quenching and non-radiative energy transferring procedure. In the acetate buffer solution with pH 7.0 and 298 K,
the quenching fluorescence intensity was in a good linearity over the concentration of drugs in the range of 1–100 μmol L−1, 0.1–100 μmol L−1, 0.5–100 μmol L−1 and 0.05–100 μmol L−1 for cefradine, cefuroxime, cefotaxime and ceftriaxone, respectively. The quenching ability or the binding ability of the
studied drugs followed the pattern: ceftriaxone > cefotaxime > cefuroxime > cefradine, which was close to the order of their
antibacterial ability. The binding parameters including the association constant and the number of binding potential point
were calculated at different temperatures (288, 298 and 308 K), and thermodynamic parameters ΔH°, ΔS° and ΔG° were given. The binding mode of lysozyme with cephalosporins showed that the hydrophobic effect might play a major role.
The binding distance between cephalosporin and tryptophan residue in lysozyme was obtained. The results provided the quantitative
information for the binding of cephalosporin to lysozyme, and it was suggested that the drugs probably bound to the active
site near Trp62 in lysozyme. 相似文献
5.
The interactions between N,N′-di(2-hydroxy-3-methyoxy-phenyl-1-methylene)-o-phenyldiamine-mone Zn(II), Nd(III) nitrate (2LZnNd) and bovine serum albumin (BSA) was investigated by various spectroscopic
techniques under physiological conditions. It was proved that the fluorescence quenching of BSA by 2LZnNb was a result of
the formation of a non-fluorescent complex with the binding constants of 3.15 × 105; 2.72 × 105 and 2.44 × 105 M–1 at 298 K, 304 K and 310 K, respectively. A marked increase in the fluorescence anisotropy in the proteinous environments
indicates that BSA introduces motional restriction on the drug molecule. The corresponding thermodynamics parameters ΔH and ΔS were calculated to be –16.36 kJ mol–1 and 43.48 J mol–1 K–1 via van’t Hoff equation. Moreover, the competitive probes experiment revealed that the binding location of 2LZnNb to BSA
is in the hydrophobic pocket of site II. The effect of 2LZnNb on the conformation of BSA has been analyzed by means of CD
spectrum and three-dimensional fluorescence spectra. The results indicate that the conformation of BSA molecules was changed
in the presence of 2LZnNb Schiff base. 相似文献
6.
The interaction between thyroxine hormone and 7 hydroxycoumarin (7HC) was investigated using fluorescence quenching method.
The experimental results showed that thyroxine could quench the fluorescence of 7HC by forming the 7HC–thyroxine complex with
static quenching. The apparent binding constants (K) between 7HC and thyroxine were determined to be 1.51 × 104 (297 K) and 9.06 × 103 (310 K). The binding sites (n) 0.98 ± 0.1. The thermodynamic parameters showed that the interaction between 7HC and thyroxine was driven mainly by hydrogen
bonding interactions and van der Waals force. Calibration for thyroxine, based on quenching titration data, was linear in
the concentration range 2.0 × 10−8 to 3.0 × 10−7 mol/l. The relative standard deviation was 2.58% for 2.0 × 10−7 mol/l thyroxine (n = 4) and the 3σ limit of detection was 3.42 × 10−8 mol/l in cationic surfactant CTAB medium. 相似文献
7.
In this paper, we reported the syntheses and investigation of the modes of binding to DNA of the two new ethidium derivatives
containing benzoyl and phenylacetyl groups of both amines at 3-and 8- positions. The interactions between calf thymus DNA
(ct-DNA) and the two derivatives, 3,8-dibenzoylamino-5-ethyl-6-phenylphenantridinium cloride (E2) and 3,8-diphenylacetylamino-5-ethyl-6-phenylphenantridinium chloride (E3), were investigated by fluorescence quenching spectra and UV-vis absorption spectra. The Stern-Volmer quenching constants,
binding constants, binding sites and the corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated at different
temperatures. The results indicated the formation of E2 and E3-DNA complexes and van der Waals interactions as the predominant intermolecular forces in stabilizing for each complex. In
addition, increasing nucleophilicity of the functional groups at 3- and 8- positions exhibited the respectable increment the
DNA binding affinities of derivatives. The results of absorption, ionic strength and iodide ion quenching suggested that the
interaction mode of E2 and E3 with ct-DNA was intercalative binding. The limit of detection (LOD) of ct-DNA were 7.49 × 10−8 (n = 4) and 4.18 × 10−8 mol/l (n = 7) in presence of E2 and E3, respectively. 相似文献
8.
In pH 1.8 ∼ 2.8 weak acid medium, polyvinylpyrrolidone (PVP) and Eosin Y reacted to form complex that could result in Eosin
Y (EY) fluorescence quenching. The maximum quenching wavelength was at 542 nm. The fluorescence quenching (ΔF) was proportional to the concentration of polyvinylpyrrolidone in a certain range. The linear range, the correlation coefficient
and the detection limit were 0.33 ∼ 2.0 μg•mL−1, 0.9994 and 99.6 ng•mL−1, respectively. The influences of the coexistence substances were tested and the results showed that the method had good selectivity.
Therefore, a new method based on fluorescence quenching of eosin Y by PVP for the determination of trace PVP was developed.
The method was sensitive, simple and rapid, which was applied to the determination of trace PVP in the beer with satisfactory
results. The reaction mechanism was also discussed. 相似文献
9.
CdHgTe nanoparticles (NPs) with the emission in the near-infrared regions were prepared in aqueous solution, and were characterized
by transmission electron microscopy, X-ray diffraction spectrometry, spectrofluorometry and ultraviolet-visible spectrometry.
Based on the fluorescence quenching of CdHgTe NPs in the presence of proteins, a novel method for the determination of proteins
with CdHgTe NPs as a near-infrared fluorescence probe was developed. Maximum fluorescence quenching was observed with the
excitation and emission wavelengths of 500 and 693 nm, respectively. Under the optimal conditions, the calibration graphs
were linear in the range of 0.04 × 10−6–5.6 × 10−6 g ml−1 for lysozyme (Lyz) and 0.06 × 10−6–6.1 × 10−6 g ml−1 for bovine hemoglobin (BHb), respectively. The limits of detection were 13 ng ml−1 for Lyz and 27 ng ml−1 for BHb, respectively. Four synthetic samples were determined and the results were satisfied. 相似文献
10.
The interaction of lysozyme with bromophenol blue (BPB) in acetate buffer (pH 6.0) was studied by fluorescence quenching method
for the first time. It was found that BPB could conspicuously quench the fluorescence of lysozyme by the static quenching
process, possibly due to the binding on the active site near Trp62. The binding parameters including the binding constant
and the number of binding site were calculated. The thermodynamic parameters ΔH°, ΔS° and ΔG° at different temperatures were obtained. The formation of lysozyme–BPB complex depended on the cooperation of the hydrophobic
and electrostatic forces. And the binding average distance between lysozyme and BPB was determined. The effect of common metal
ions on the binding constant of lysozyme–BPB was also examined. 相似文献
11.
Azab HA Duerkop A Mogahed EM Awad FK Abd El Aal RM Kamel RM 《Journal of fluorescence》2012,22(2):659-676
This work describes the application of time resolved fluorescence in microtiterplates and electrochemical methods on glassy
carbon electrode for investigating the interactions of europium-3-carboxycoumarin with pesticides aldicarb, methomyl and prometryne.
Stern-volmer studies at different temperatures indicate that static quenching dominates for methomyl, aldicarb and prometryne.
By using Lineweaver-Burk equation binding constants were determined at 303 K, 308 K and 313 K. A thermodynamic analysis showed
that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined.
A time-resolved (gated) luminescence-based method for determination of pesticides in microtiterplate format using the long-lived
europium-3-carboxycoumarin has been developed. The limit of detection is 4.80, 5.06 and 8.01 μmol L−1 for methomyl, prometryne and aldicarb, respectively. This is the lowest limit of detection achieved so far for luminescent
lanthanide-based probes for pesticides. The interaction of the probe with the pesticides has been investigated using cyclic
voltammetry (CV), differential pulse polarography (DPP), square wave voltammetry (SWV) and linear sweep voltammetry (LSV)
on a glassy carbon electrode in I = 0.1 mol L−1 p-toluenesulfonate at 25 °C. The diffusion coefficients of the reduced species are calculated. The main properties of the
electrode reaction occurring in a finite diffusion space are the quasireversible maximum and the splitting of the net SWV
peak for Eu(III) ions in the ternary complex formed . It was observed that the increase of the cathodic peak currents using
LSV is linear with the increase of pesticides concentration in the range 5 × 10−7 to 1 × 10−5 mol L−1. The detection limit (DL) were about 1.01, 2.23 and 1.89 μmolL−1 for aldicarb, methomyl and prometryne, respectively. In order to assess the analytical applicability of the method, the influence
of various potentially interfering species was examined. Influence of interfering species on the recovery of 10 μmol L−1 pesticides has been investigated. 相似文献
12.
A sensitive and selective method for the trace determination of 3, 3’, 4, 4’-tetrachlorobiphenyl (PCB77) by using bovine serum
albumin (BSA) as a fluorescence probe was introduced. Under optimum conditions, the enhanced fluorescence intensity was proportional
to the concentration of polychlorinated biphenyls in the range of 8.9 × 10−8–5.0 × 10−6 mol L−1 for PCB77, and 5.0 × 10−7–5.0 × 10−6 mol L−1 for 2, 2’, 5, 5’-tetrachlorbiphenyl (PCB52). The detection limits (S/N = 3) of PCB77 and PCB52 were 2.6 × 10−8 mol L−1 and 2.9 × 10−7 mol L−1, respectively. Furthermore, the fluorescence enhancement mechanism was discussed in detail. Results indicated that fluorescence
enhancement of the system originated from the formation of BSA-PCBs complexes. In addition, PCBs were mainly bound to the
tyrosine residues in BSA molecules. 相似文献
13.
The saccharide binding and conformational characterization of a hemagglutinin, a low molecular weight protein from the seeds
of Moringa oleifera was studied using steady state and time resolved fluorescence. The lectin binds sugars LacNAc (K
a = 1380 M−1) and fructose (K
a = 975 M−1), as determined by the fluorescence spectroscopy. It has a single tryptophan per monomer which is exposed on the surface
and is in a strong electropositive environment as revealed by quenching with iodide. Quenching of the fluorescence by acrylamide
involved both static (K
s = 0.216 M−1) and collisional (K
sv = 8.19 M−1) components. The native protein showed two different lifetimes, τ
1 (1.6 ns) and τ
2 (4.36 ns) which decrease and get converted into a single one, (2.21 ns) after quenching with 0.15 M acrylamide. The bimolecular
quenching constant, k
q
was 7.55 × 1011 M−1 s−1. ANS binding studies showed that the native protein has exposed hydrophobic patches which get further exposed at extreme
acidic or alkaline pH. However, they get buried in the interior of the protein in presence of 1 M GdnHCl or urea. 相似文献
14.
In this paper we reported a metal complex 1-Zn (2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine-4-hydroxy-phenyl)-ethylene]-pyrazine-Zn) as a fluorescent probe sensing DNA. The
result of the competitive experiment of the probe with ethidium bromide (EB) to bind DNA, absorption spectral change and polarization
change in the presence and absence of DNA revealed that interaction between the probe and DNA was via intercalation. Ionic
strength experiment showed the existence of electrostatic interaction as well. Scatchard plots also confirmed the combined
binding modes. The fluorescence enhancement of the probe was ascribed to highly hydrophobic environment when it bound the
macromolecules such as DNA, RNA or denatured DNA. The binding constant between the probe and DNA was estimated as 3.13 × 107 mol−1 L. The emission intensity increase was proportional to the concentration of DNA. Based on this, the probe was used to determine
the concentration of calf thymus DNA (ct-DNA). The corresponding linear response ranged from 2.50 × 10−7 to 4.75 × 10−6 mol L−1, and detection limit was 1.93 × 10−8 mol L−1 for ct-DNA. 相似文献
15.
The serum albumin is the most abundant protein in blood plasma and the iron is essential for many cellular processes. However,
the interaction between Fe3+ and haem-free serum albumin remains unclear. Here we provide evidence for the fact that haem-free BSA possesses one specific
Fe3+-binding site. The binding of Fe3+ to BSA results in a significant quenching of the Trp fluorescence of BSA. The average apparent dissociation constant value
for the interaction of Fe3+ and BSA is 3.46 × 10−8 ± 3 × 10−10 M at 37 °C and 3.30 × 10−8 ± 5 × 10−10 M at 25 °C, respectively, as determined by fluorescence titration. Addition of 50 μM Fe2+ to 1 μM BSA results in an obvious hysteretic effect on the fluorescence of BSA. The time-dependent fluorescence quenching
of BSA by Fe2+ is not caused by the Fe2+-induced conformational change of BSA, but the oxygen-dependent oxidation of Fe2+ to Fe3+. Fe2+ undergoes an oxygen-dependent oxidation to Fe3+ under aerobic conditions, which is accelerated by the interaction of BSA with Fe3+ and extensively inhibited under anaerobic conditions. The results suggest that BSA may take part in non-transferrin bound
iron transfer. 相似文献
16.
The specific heat of undercooled liquid Ni80Fe10Cu10 alloy was experimentally measured by electromagnetic levitation drop calorimeter, and also numerically simulated by the molecular
dynamics method. The achieved maximum undercooling is up to 252 K (0.15 T
L) in the experiments, and the measured result is 41.67 J mol−1 K−1. The simulation provides calculated data within 0∼702 K undercooling range, which is much broader than the experimental regime.
The simulated value is 37.02 J mol−1 K−1. Although there exists a difference of 4.65 J mol−1 K−1 between them, the result is quite acceptable for simulation. Furthermore, the liquid structure of undercooled Ni80Fe10Cu10 alloy is studied in terms of the total and partial pair distribution functions, which display that the ordered degree of
atoms enhances from a normal liquid to metastable state. 相似文献
17.
Bruno B. Campos Manuel Algarra Joaquim C. G. Esteves da Silva 《Journal of fluorescence》2010,20(1):143-151
A fluorescent hybrid cadmium sulphide quantum dots (QDs) dendrimer nanocomposite (DAB-CdS) synthesised in water and stable
in aqueous solution is described. The dendrimer, DAB-G5 dendrimer (polypropylenimine tetrahexacontaamine) generation 5, a
diaminobutene core with 64 amine terminal primary groups. The maximum of the excitation and emission spectra, Stokes’ shift
and the emission full width of half maximum of this nanocomposite are, respectively: 351, 535, 204 and 212 nm. The fluorescence
time decay was complex and a four component decay time model originated a good fit (χ = 1.20) with the following lifetimes: τ
1 = 657 ps; τ
2 = 10.0 ns; τ
3 = 59.42 ns; and τ
4 = 265 ns. The fluorescence intensity of the nanocomposite is markedly quenched by the presence of nitromethane with a dynamic
Stern-Volmer constant of 25 M−1. The quenching profiles show that about 81% of the CdS QDs are located in the external layer of the dendrimer accessible
to the quencher. PARAFAC analysis of the excitation emission matrices (EEM) acquired as function of the nitromethane concentration
showed a trilinear data structure with only one linearly independent component describing the quenching which allows robust
estimation of the excitation and emission spectra and of the quenching profiles. This water soluble and fluorescent nanocomposite
shows a set of favourable properties to its use in sensor applications. 相似文献
18.
It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU) - cetyltrimethylammonium
bromide (CTAB) – nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence
intensity is proportion to the concentration of nucleic acids in the range of 2.0 × 10−8–1.0 × 10−6 g mL−1 for fish sperm DNA (fsDNA), 2.0 × 10−8–1.0 × 10−6 g mL−1 for calf thymus DNA (ctDNA), 1.0 × 10−8–1.0 × 10−6 g mL−1 for yeast RNA (yRNA), and their detection limits (S/N = 3) are 8.0 ng mL−1, 10.5 ng mL−1 and 5.8 ng mL−1, respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The
interaction mechanism is also studied. 相似文献
19.
20.
L-Cysteine capped CdTe nanoparticles (NPs) were synthesized in aqueous medium, and their application as fluorescence probes
in the determination of paracetamol was studied. The L-cysteine capped CdTe NPs were characterized by transmission electron
microscopy, X-ray diffraction spectrometry, spectrofluorometry, ultraviolet-visible and Fourier transform infrared spectrometry.
Based on the distinct fluorescence quenching of CdTe fluorescence probes in the presence of paracetamol, a simple, rapid and
specific method for paracetamol determination was presented. Under optimum conditions, the relative fluorescence intensity
of CdTe NPs was linearly proportional to paracetamol concentration from 1.0 × 10−8 mol/L to 1.6 × 10−7 mol/L with a detection limit of 4.2 × 10−9 mol/L. The proposed method was applied to detect paracetamol in commercial tablets with satisfactory results. 相似文献