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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.
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
3.
Marcolan M Martins PA Pedrosa VA Rodrigues MR de Oliveira HP Codognoto L 《Journal of fluorescence》2011,21(2):733-738
A simple, rapid and effective analytical method based on fluorescence spectroscopy for the determination of coumarin in pharmaceutical
formulations without pre-treatment or pre-concentration step was development. Coumarin had maximum excitation and emission
at 310 nm and 390 nm, respectively. Optimum conditions for the detection of coumarin were investigated. Under optimized conditions,
we observed a linear behavior for the sign of coumarin in the concentration range of 2.5 × 10−6 to 1.0 × 10−4 mol L−1, with linearity of 0.998 and sensitivity of 2.9 × 1010 u.a/mol L−1. The proposed method was validated in terms of accuracy, precision and specificity of coumarin using the standard addition
and external calibration. It was noted that the results support (P < 0.05), indicating that the matrices were not an interference in the determination of coumarin by fluorescence spectroscopy.
The results were favorable compared with those obtained by reference chromatographic methods. 相似文献
4.
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
5.
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
6.
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
7.
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
8.
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
9.
Hosseini M Ganjali MR Tavakoli M Norouzi P Faridbod F Goldooz H Badiei A 《Journal of fluorescence》2011,21(4):1509-1513
A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal
complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)2Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10−7 to 1.0 × 10−5 mol/L of PPi and the detection limit of 2.3 × 10−8 mol/L. The association constant of L-PPi complex was calculated 2.6 × 105 L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I3-, NO3-, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which was attributed to higher stability of inorganic complex between pyrophosphate and L. 相似文献
10.
In our study, terbium-acetylacetone (Tb-acac) composite nanoparticles have been prepared under vigorous ultrasonic irradiation.
The nanoparticles are water soluble, stable and have extremely narrow emission bands and high internal quantum efficiencies.
They were used as fluorescence probes in the determination of enoxacin (Enox) based on the fluorescence enhancement of nanoparticles
through fluorescence resonance energy transfer (FRET). The influence of buffer solution on the fluorescence intensity was
investigated. Under the optimum conditions, the fluorescence intensity of the Tb-acac-Enox system is linearly proportional
to the Enox concentration in the Enox concentration range of 2 × 10−7–1 × 10−4 M. The correlation coefficient for the calibration curve was 0.9976. The limit of detection as defined by IUPAC, C
LOD = 3S
b/m (where S
b is the standard deviation of the blank signals and m is the slope of the calibration graph) was found to be 3 × 10−8 M. The relative standard deviation (RSD) for six repeated measurements of 1 × 10−4 M Enox was 1.35%. The method was applied to the determination of Enox in pharmaceutical formulation and recovery results
were obtained from urine samples. 相似文献
11.
12.
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
13.
Water-soluble Mn2+-doped ZnS quantum dots (QDs) were prepared using mercaptoacetic acid as the stabilizer. The optical properties and structure
features were characterized by X-Ray, absorption spectrum, IR spectrum and fluorescence spectrum. In pH 7.8 Tris-HCl buffer,
the QDs emitted strong fluorescence peaked at 590 nm with excitation wavelength at 300 nm. The presence of sulfide anion resulted
in the quenching of fluorescence and the intensity decrease was proportional to the S2− concentration. The linear range was from 2.5 × 10−6 to 3.8 × 10−5 mol L−1 with detection limit as 1.5 × 10−7 mol L−1. Most anions such as F−, Cl−, Br−, I−, CH3CO2
−, ClO4
−, CO3
2−, NO2
−, NO3
−, S2O3
2−, SO3
2− and SO4
2− did not interfere with the determination. Thus a highly selective assay was proposed and applied to the determination of
S2− in discharged water with the recovery of ca. 103%. 相似文献
14.
A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in
which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified
as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized
acidic sulphate medium (i.e., 0.3 M H2SO4 and 0.7 M Na2SO4) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited
strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant
power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10−7–1.0 × 10−5 M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox,
quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine.
The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox
equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those
found by reference methods such as ABTS and CUPRAC. 相似文献
15.
A complex Fe(phen)2·PHPIP·3ClO4·2H2O, where phen = 1,10-phenanthroline and PHPIP = p-hydroxyphenylimidazo[f]1,10-phenanthroline, was synthesized and acted as a good fluorescence indicator based on its interaction
with double-duplex DNA. Then a fiber-optic DNA biosensor of fluorimetric detection was developed based on the recognition
of target DNA in DNA hybridization assays. A probe ssDNA was covalently immobilized onto the surface of quartz optical fibers
and then the probe ssDNA hybridized with complementary ssDNA introduced into the local environment of the sensor. The hybridization
with complementary strands was monitored in real time by fluorimetric detection. Several factors affecting the probe immobilization,
target DNA hybridization, and indicator binding reactions were optimized to maximize the sensitivity and shorten the assay
time. Using this method, a sequence of the 16-mer oligonucleotides could be quantified over the range from 4.98 × 10−7 to 4.88 × 10−6 M and a detection limit of 1.08 × 10−7 M. And the designed optic-fiber biosensor could be conveniently regenerated by thermal denature. The utility of the novel
hybridization indicator could provide a simple, rapid, low toxicity and reusable detection. 相似文献
16.
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
17.
Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker
separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties.
The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices
such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed
in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform
and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and
methanol. The fluorescence lifetimes are in the range of 1–4 ns for all measured fluorophores. The large Stokes shift (4,000
to 8,000 cm−1) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The
observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by
the diffusion-controlled bimolecular rate (cca 2 × 1010 L mol−1 s−1). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism. 相似文献
18.
A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of
chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The
chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel
matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration
of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone
or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10−9–1 × 10−4 and 1 × 10−8–7 × 10−5 mol L−1, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10−10 , 9.6 × 10−10 and 5.6 × 10−10, 1.7 × 10−9 mol L−1, respectively. 相似文献
19.
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
20.
L. Ciaffoni B. L. Cummings W. Denzer R. Peverall S. R. Procter G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2008,92(4):627-633
High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different
transitions within the region of the ν
1+ν
2+ν
3 and 2ν
1+ν
2 combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross
sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using
cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H2S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy
(WMS). The set-up sensitivity has been calculated as 1.73×10−8 cm−1 s1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions
has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated
to the intermolecular potentials governing the collision process; the H2S–H2S dimer well depth is estimated to be 7.06±0.09 kJ mol−1. 相似文献