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1.
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
2.
M.?Cristina?Gon?alves Verónica?de?Zea Bermudez M.?M.?Silva M.?J.?Smith Enrique?Morales Rute?A.?Sá Ferreira Luís?D.?Carlos 《Ionics》2010,16(3):193-201
Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application
of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y′), where Y′ indicates the average
molecular weight of the polymer segment), were doped with lithium triflate (LiCF3SO3). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH2CH2) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH2CH2) repeat units per Li+), are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 °C. At room temperature the conductivity
maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0 × 10−6 and 7.4 × 10−5 Scm−1, respectively). At about 100 °C, both these samples also exhibit the highest conductivity of the two electrolyte systems
(approximately 1.6 × 10−4 and 1.0 × 10−3 Scm−1, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability. 相似文献
3.
A. V. Zabrodin 《JETP Letters》1997,66(9):653-659
Local M operators for the classical sine-Gordon model in discrete space-time are constructed by convolution of the quantum trigonometric
4×4 R matrix with certain vectors in its “quantum” space. Components of the vectors are τ functions of the model. This construction
generalizes the known representation of continuous-time M operators in terms of the classical r matrix.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 620–625 (10 November 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
4.
In this work, a new simple and sensitive flow injection method is developed for the determination of homocysteine with spectrofluorimetric
detection technique. This method is based on the oxidation of homocysteine with Tl (III) in acidic media, producing fluorescence
reagent, TlCl32- (λex = 237 nm, λem = 419 nm). The effects of chemical parameters (including pH of the solutions, the buffer, Tl (III) and potassium chloride
concentrations), instrumental parameters (such as flow rate of the solutions, reaction coil length, and sample loop volume)
and temperature on the fluorescence intensity as an analytical signal are studied and optimized. In the optimum conditions
of the above variables, homocysteine can be determined in the range 4.0 × 10-7–40.0 × 10-6 M with the LDR from 4.0 × 10-7 to 25.0 × 10-6 M. The detection limit (with S/N = 3) is 6.0 × 10-8 M of homocysteine and precision for the injection of 5.0, 10.0 and 15.0 μM of homocysteine are 0.8%, 1.5% and 2.5% (n = 10) respectively. The rate of analysis is 90 samples per hour. The influence of potential interfering substances, including
amino acids and carbohydrates is also studied. The proposed method has been successfully used for the determination of homocysteine
in the real sample (blood serum and tap water) matrix. 相似文献
5.
Alonso A Almendral MJ Curto Y Criado JJ Rodríguez E Manzano JL 《Journal of fluorescence》2007,17(4):390-400
The flow injection technique is applied to study the binding to DNA of new platinum complexes—E1: ethylenediaminechlorocholylglycinateplatinum(II): [PtCl(CG)(en)], C54H92O12Pt and E2: ethylenediaminebischolylglycinateplatinum(II): [Pt(CG)2(en)], C28H50ClN3O6Pt—derived from cisplatin in which the exchangeable ligands were replaced by bile acids, such that these anticancer drugs
have less toxicity and less resistance is developed towards them. Both compounds are fluorescent and their fluorescence is
enhanced when they form adducts with DNA, a property that is extremely useful for monitoring the cytotoxic activity and their
mechanisms of action. The binding parameters to DNA of E1 [apparent intrinsic binding constant KE1: (11.2 ± 0.4) × 103 M−1 and maximum number of binding sites per nucleotide, n
E1: 0.121 ± 2 × 10−3) and E2 (KE2: 9.2 ± 0.7) × 103 M−1 and n
E2 0.098 ± 2 × 10−3] were determined following the Scatchard method and the type of binding was studied experimentally through the modifications
introduced by each of the compounds into the ethidium bromide–DNA bond. 相似文献
6.
Françoise Lust-Piquard 《Communications in Mathematical Physics》1999,205(3):519-549
The Fock Von Neumann algebra , equipped with its canonical trace τ, is spanned by n hermitian operators acting on a Hilbert Fock space some commutation relations between and are defined by the n×n hermitian matrix A. We define a Riesz transform , where is the number operator, ∇′ is aninner derivation (unbounded in general) and . Let 1<p<∞. We prove that is equivalent to for every with null trace, with constants which do not depend on n.
Received: 24 November 1998 / Accepted: 2 March 1999 相似文献
7.
K. J. Oyewumi 《International Journal of Theoretical Physics》2010,49(6):1302-1316
The dynamical symmetries of the Kratzer-type molecular potentials (generalized Kratzer molecular potentials) are studied by
using the factorization method. The creation and annihilation (ladder) operators for the radial eigenfunctions satisfying
quantum dynamical algebra SU(1,1) are established. Factorization method is a very simple method of calculating the matrix elements from these ladder operators.
The matrix elements of different functions of r,
r\fracddrr\frac{d}{dr}, their sum Γ1 and difference Γ2 are evaluated in a closed form. The exact bound state energy eigenvalues E
n,ℓ
and matrix elements of r,
r\fracddrr\frac{d}{dr}, their sum Γ1 and difference Γ2 are calculated for various values of n and ℓ quantum numbers for CO and NO diatomic molecules for the two potentials. The results obtained are in very good agreement with those obtained by other methods. 相似文献
8.
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
9.
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
10.
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
11.
Random Hermitian matrices are used to model complex systems without time-reversal invariance. Adding an external source to
the model can have the effect of shifting some of the matrix eigenvalues, which corresponds to shifting some of the energy
levels of the physical system. We consider the case when the n×n external source matrix has two distinct real eigenvalues: a with multiplicity r and zero with multiplicity n−r. For a Gaussian potential, it was shown by Péché (Probab. Theory Relat. Fields 134:127–173, 2006) that when r is fixed or grows sufficiently slowly with n (a small-rank source), r eigenvalues are expected to exit the main bulk for |a| large enough. Furthermore, at the critical value of a when the outliers are at the edge of a band, the eigenvalues at the edge are described by the r-Airy kernel. We establish the universality of the r-Airy kernel for a general class of analytic potentials for r=O(ng)r=\mathcal{O}(n^{\gamma}) for 0≤γ<1/12. 相似文献
12.
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
13.
A biopolymer electrolyte system having conductivity ∼1.3 × 10−4 S cm−1 has been prepared using potato starch, NaI, glutaraldehyde and poly(ethylene glycol) (PEG; molecular weight = 300). High
ionic transference numbers (∼0.99) of the material confirmed its electrolytic behaviour. Conductivity and dielectric behaviour
as a function of frequency has been studied. Conductivity follows ‘universal power law’ (σ = σ
0 + Aω
n
) with exponent ‘n’ varying from 0.94 to 1.18. Cross-linking and plasticization increases long pathways motion of charge carriers, comparable
to sample dimension. Humidity-independent behaviour (up to 80% relative humidity), of impedance and water intake by the system,
indicates the system’s potentiality as a promising candidate for humidity immune device fabrication. The addition of PEG has
a twofold effect on the material’s conductivity. It not only increases conductivity but also improves the material’s immunity
towards humid atmosphere. 相似文献
14.
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
15.
By means of a transfer matrix method, we show that the residual entropy S of the two-dimensional square lattice antiferromagnetic Ising model in the maximal critical field satisfies (ln λ
n
)/(n+1)≤S≤(ln λ
n
)/n, where λ
n
is the largest eigenvalue of the transfer matrix F
n
on a strip of width n. Using these bounds, we numerically calculate the value of S, with precise estimates on the errors, namely, S=0.394198±0.020747. 相似文献
16.
Hybrid membranes doped with silicotungstic acid (STA) were prepared by sol–gel process with 3-glycidoxypropyltrimethoxysilane,
3-aminopropyltriethoxysilane, phosphoric acid, and tetraethoxysilane as chemical precursors. The thermogravimetry and differential
thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 350 °C. Relatively, a high proton
conductivity of 2.85 × 10−2 S/cm was obtained for 10 mol% STA-doped hybrid membrane at 120 °C under 90% RH. The hydrogen permeability was found to decrease
in the temperature range 20–120 °C from 1.64 × 10−10 to 1.36 × 10−10 mol/cm.s.Pa. 相似文献
17.
A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous
analysis of binary mixture of cinnarizine (CN) and domperidone (DOM). The method is based upon measurement of the native fluorescence
of these drugs at Δλ = 80 nm in aqueous methanol (50% V/V). The different experimental parameters affecting the native fluorescence
of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the
range of 0.1 to 1.3 μg mL−1 and 0.1–3.0 μg mL−1 for CN and DOM, respectively with lower detection limits of 0.017 and 5.77 × 10−3 μg mL−1 and quantification limits of 0.058 and 0.02 μg mL−1 for CN and DOM. The proposed method was successfully applied for the determination of the studied compounds in synthetic
mixtures and in commercial tablets. The results obtained were in good agreement with those obtained with reference methods.
The high sensitivity attained by the synchronous fluorometric method allowed the determination of CN in real and spiked human
plasma. The mean % recoveries in case of spiked human plasma (n = 3) were 96.39 ± 1.18 while that in real human plasma (n = 3) was 104.67 ± 4.16. 相似文献
18.
Ion-conducting thin film polymer electrolytes based on poly(ethylene oxide) (PEO) complexes with NaAlOSiO molecular sieves
powders has been prepared by solution casting technique. X-ray diffraction, scanning electron microscopy, differential scanning
calorimeter, and alternating current impedance techniques are employed to investigate the effect of NaAlOSiO molecular sieves
on the crystallization mechanism of PEO in composite polymer electrolyte. The experimental results show that NaAlOSiO powders
have great influence on the growth stage of PEO spherulites. PEO crystallization decrease and the amorphous region that the
lithium-ion transport is expanded by adding appropriate NaAlOSiO, which leads to drastic enhancement in the ionic conductivity
of the (PEO)16LiClO4 electrolyte. The ionic conductivity of (PEO)16LiClO4-12 wt.% NaAlOSiO achieves (2.370 ± 0.082) × 10−4 S · cm−1 at room temperature (18 °C). Without NaAlOSiO, the ionic conductivity has only (8.382 ± 0.927) × 10−6 S · cm−1, enhancing 2 orders of magnitude. Compared with inorganic oxide as filler, the addition of NaAlOSiO molecular sieves powders
can disperse homogeneously in the electrolyte matrix without forming any crystal phase and the growth stage of PEO spherulites
can be hindered more effectively. 相似文献
19.
A fluorescent assay of Hg2+ in neutral aqueous solution was developed using N-[p-(dimethylamino)benzamido]-N′-phenylthiourea (1). 1’s fluorogenic chemodosimetric behaviors towards various metal ions were studied and a high sensitivity
as well as selectivity was achieved for Hg2+. It was because of a strongly fluorescent 1,3,4-oxadiazoles which was produced by the Hg2+ promoted desulfurization reaction. The spectra of ESI mass and IR provided evidences for this reaction. According to fluorescence
titration, a good linear relationship ranging from 1.0 × 10−7 to 2.0 × 10−5 mol l−1 was obtained with the limit of detection as 3.1 × 10−8 mol l−1.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
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