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1.
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
2.
The interaction of a N-methylated diaminotriphenylmethane dye, malachite green, with lysozyme was investigated by fluorescence spectroscopic techniques
under physiological conditions. The binding parameters have been evaluated by fluorescence quenching methods. The results
revealed that malachite green caused the fluorescence quenching of lysozyme through a static quenching procedure. The thermodynamic
parameters like ΔH and ΔS were calculated to be −15.33 kJ mol−1 and 19.47 J mol−1 K−1 according to van’t Hoff equation, respectively, which proves main interaction between malachite green and lysozyme is hydrophobic
forces and hydrogen bond contact. The distance r between donor (lysozyme) and acceptor (malachite green) was obtained to be 3.82 nm according to Fӧrster’s theory. The results
of synchronous fluorescence, UV/vis and three-dimensional fluorescence spectra showed that binding of malachite green with
lysozyme can induce conformational changes in lysozyme. In addition, the effects of common ions on the constants of lysozyme-malachite
green complex were also discussed. 相似文献
3.
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
4.
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
5.
Su-Zhen Hao Si-Dong Liu Xiao-Hong Wang Xiu-Jun Cui Li-Ping Guo 《Journal of luminescence》2009,129(11):1320-1325
The interaction of Na9[SbW9O33]·19.5H2O (SbW) with bovine serum albumin (BSA) is studied by spectroscopic and voltammetric methods. Absorption spectroscopy of BSA and the linear sweep voltammetry of SbW proved the formation of ground-state SbW–BSA complex. Fluorescence quenching of serum albumin by SbW is also found to be a static quenching process. The binding constant Ka is 4.13×104 L mol−1 for SbW–BSA at pH 7.40 Tris–HCl buffer at 295 K. The number of binding sites and the apparent binding constants at different temperatures are obtained from the analysis of the fluorescence quenching data. The thermodynamic parameters determined by the Van’t Hoff analysis of the binding constants (ΔH=−80.01 kJ mol−1 and ΔS=−182.85 J mol−1 K−1) clearly show that the binding is absolutely entropy driven. Hydrogen bonding and van der Waals interaction force play major role in stabilizing the complex. The effect of SbW on the conformation of BSA is analyzed using synchronous fluorescence spectroscopy. 相似文献
6.
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
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.
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
9.
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
10.
The luminescence arising from lanthanide cations offers several advantages over organic fluorescent molecules: sharp, distinctive
emission bands allow for easy resolution between multiple lanthanide signals; long emission lifetimes (μs –ms) make them excellent
candidates for time-resolved measurements; and high resistance to photo bleaching allow for long or repeated experiments.
A method is presented for determination of nucleosides using the effect of enhancement of fluorescence of the easily accessible
europium(III)-TNB in presence of different nucleosides. The latter coordinates to Eu(III) -TNB and enhances its luminescence
intensity as a result of the displacement of water from the inner coordination sphere of the central metal. A similar method
for the determination of DNA based on the quenching of Eu(III)-TNB has been established. The interaction of Eu(III)-4,4,4
trifluoro-1-(2-naphthyl)1,3-butanedione (TNB) complex with nucleosides (NS) (guanosine, adenosine, cytidine , inosine) and
DNA has been studied using normal and time-resolved luminescence techniques. Binding constants were determined at 293 K, 298 K,
303 K, 308 K and 313 K by using Benesi-Hildebrand equation. 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. The formation of binary and ternary
complexes of Eu (III) with nucleosides and TNB has been studied potentiometrically at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol.dm−3 (KNO3) . The formation of the 1:1 binary and 1:1:1 ternary complexes are inferred from the corresponding titration curves. Initial
estimates of the formation constants of the resulting species and the protonation constants of the different ligands used
have been refined with the HYPERQUAD computer program. Electrochemical investigations for the systems under investigations
have been carried out using cyclic voltammetry (CV), differential pulse polarography (DPP), and square wave voltammetry (SWV)
on a glassy carbon electrode in I = 0.1 mol/L p-toluenesulfonate as supporting electrolyte. 相似文献
11.
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
12.
Suthari Prashanthi P. Hemant Kumar Li Wang Arun Kumar Perepogu Prakriti Ranjan Bangal 《Journal of fluorescence》2010,20(2):571-580
Steady state and time resolved fluorescence quenching behaviors of meso-Tetrakis (pentafluorophenyl) porphyrin (H2F20TPP) in presence of different aliphatic and aromatic amines have been executed in homogeneous dichloromethane (DCM) solution.
At room temperature in DCM, free base (H2F20TPP) shows fluorescence with two distinct peaks at 640 and 711 nm and natural lifetime τ
f = 9.8 ns which are very similar to that of meso-tetraphenyl porphyrin (TPP). Unlike TPP, addition of both aliphatic and aromatic
amines to a solution containing H2F20TPP results in an efficient decrease in fluorescence intensity without altering the shape and peak position of fluorescence
emission. Upon addition of amines there was no change in optical absorption spectra of H2F20TPP. The fluorescence quenching rate constants ranged from 1 × 109 to 4 × 109 s−1, which are one order below to the diffusion control limit, and temperature dependent quenching rate constants yield the activation
energies which are found to be order of 0.1 eV. Femto second transient absorption studies reveal the existence of amine cation
radical and porphyrin anion radicals with very short decay time (15 ps). The fluorescence quenching reaction follows Stern–Volmer
kinetics. Steady state and time-resolved data are interpreted within general kinetic scheme of Marcus semi-classical model
which attributes bimolecular electron transfer process between amines and the lowest excited singlet state of H2F20TPP. Calculated internal reorganization energies are found to be in between 0.04 and 0.22 ev. Variation of electron transfer
rate as function of free energy change (∆G0) points the ET reactions in the present systems are in Marcus normal region. This is the first example of reductive fluorescence
quenching of free base neutral porphyrins in homogeneous organic solvent ever known. 相似文献
13.
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
14.
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
15.
Sreejith RK Suresh CG Bhosale SH Bhavnani V Kumar A Gaikwad SM Pal JK 《Journal of fluorescence》2012,22(1):431-441
In mammalian cells, the heme-regulated inhibitor (HRI) plays a critical role in the regulation of protein synthesis at the
initiation step through phosphorylation of α-subunit of the eukaryotic initiation factor 2 (eIF2). In this study we have cloned
and performed biophysical characterization of the kinase catalytic domain (KD) of rabbit HRI. The KD described here comprises
kinase 1, the kinase insertion domain (KI) and kinase 2. We report here the existence of an active and stable monomer of HRI
(KD). The HRI (KD) containing three tryptophan residues was examined for its conformational transitions occurring under various
denaturing conditions using steady-state and time-resolved tryptophan fluorescence, circular dichroism (CD) and hydrophobic
dye binding. The parameter A and phase diagram analysis revealed multi-state unfolding and existence of three stable intermediates
during guanidine hydrochloride (Gdn-HCl) induced unfolding of HRI (KD). The protein treated with 6 M Gdn-HCl showed collisional
and static mechanism of acrylamide quenching and the constants (K
sv
= 3.08 M−1and K
s
= 5.62 M−1) were resolved using time resolved fluorescence titration. Based on pH, guanidine hydrochloride and temperature mediated
transitions, HRI (KD) appears to exemplify a rigid molten globule-like intermediate with compact secondary structure, altered
tertiary structure and exposed hydrophobic patches at pH 3.0. The results indicate the inherent structural stability of HRI
(KD), a member of the class of stress response proteins. 相似文献
16.
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
17.
The effect of Pb2+ targeted to bovine serum albumin (BSA) in vitro was investigated by fluorescence, synchronous fluorescence, UV absorption
and circular dichroism (CD) spectrophotometry. The characteristic fluorescence of BSA was quenched, which indicated that Pb2+ changed the skeleton of BSA and caused the gradual exposure of aromatic amino acid residues (Trp, Tyr, Phe) in the internal
hydrophobic region of BSA. When the concentration of Pb2+ was higher than 1 × 10−4 mol/L, the BSA was completely denatured. The excess lead ion interacted with the aromatic amino acid residues of BSA exposed
to the solution, which decreased the fluorescence of BSA further. According to the experiment results, we found that a lead-BSA
complex was formed following static quenching and the binding site was calculated approximately equal to 1. This work reflected
the interaction mechanism of BSA and Pb2+ from the perspective of spectroscopy. 相似文献
18.
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
19.
Fengling Cui Qiangzhai Zhang Yinghua Yan Xiaojun Yao Guirong Qu Yan Lu 《Journal of Applied Spectroscopy》2008,75(5):743-751
The interactions of human (HSA) and bovine (BSA) serum albumins with 1-cyanoethyl-5-chlorouracil (CECU) were investigated
by fluorescence spectroscopy, UV absorption spectroscopy, and molecular modeling methods under the simulated physiological
conditions. The results of fluorescence measurements indicate that CECU has a strong ability to quench the intrinsic fluorescence
of both HSA and BSA through a static quenching procedure. The binding constants (K) at different temperatures and thermodynamic
parameters, enthalpy change (ΔH), and entropy change (ΔS) were calculated according to fluorescence data. The results show
that hydrophobic interaction is a predominant intermolecular force for stabilizing the complex, which is in agreement with
the results of molecular modeling study. The effect of some normal ions on the binding constants is also discussed.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 737–745, September–October, 2008. 相似文献
20.
Wen Xiu Li 《光谱学快报》2013,46(4):210-216
ABSTRACT The interaction of isoquercitrin and bovine serum albumin (BSA) was investigated by means of fluorescence spectroscopy (FS), resonance light scattering spectroscopy (RLS), and ultraviolet spectroscopy (UV). The apparent binding constants (K a) between isoquercitrin and BSA were 5.37 × 105 L mol?1 (293.15 K) and 2.34 × 105 L mol?1 (303.15 K), and the binding site values (n) were 1.18 ± 0.03. According to the Förster theory of non-radiation energy transfer, the binding distances (r) between isoquercitrin and BSA were 1.94 and 1.95 nm at 293.15 K and 303.15 K, respectively. The experimental results showed that the isoquercitrin could be inserted into the BSA, quenching the inner fluorescence by forming the isoquercitrin–BSA complex. The addition of increasing isoquercitrin to BSA solution leads to the gradual enhancement in RLS intensity, exhibiting the formation of the aggregate in solution. It was found that both static quenching and non-radiation energy transfer were the main reasons for the fluorescence quenching. The entropy change and enthalpy change were negative, which indicated that the interaction of isoquercitrin and BSA was driven mainly by van der Waals interactions and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. 相似文献