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1.
K. H. Standke 《Journal of Radioanalytical and Nuclear Chemistry》1976,32(2):447-459
Calibration of a counting rate method with standard solutions of14C-labelled peptides allows the accurate determination of 1·10−6 to 1·10−2M concentrations of peptides in aqueous solution. By the use of this method and the equilibrium dialysis technique it is shown
that binding constants of different peptides to DNA that differ by as little as ΔK=|0.3|mM−1 can be measured. Statistical error considerations show that such a result is significant. The use of colored complexes formed
between 2,4-dinitrofluorobenzene and LYS-LYS and LYS-TRYP-LYS enabled the affinity constants of these peptides with calf-thymus
DNA to be determined. The advantages of the determination of peptide concentrations, by the use of radioactive counting, over
colorimetric methods as well as the importance of this highly sensitive method for the measurement of peptide concentrations
and hence binding constants are discussed. 相似文献
2.
The ability of DNA to extract fluoroquinolones from model solutions and real probes of food was demonstrated and investigated
quantitatively. The interaction between fluoroquinolones and different types of DNA was studied by equilibrium dialysis. The
first application of this direct approach allowed us to determine binding constants and binding stoichiometries in different
conditions. The binding of enrofloxacin to heat-denatured DNA (d-DNA) from herring sperm is pH- and magnesium-dependent; the
highest fraction of bound drugs was found at pH 7 and a magnesium concentration of 0.5–1 mM. Results for three types of DNA:
d-DNA, double-stranded DNA and single-stranded DNA were compared. The unwound DNA showed almost doubled binding constants
and stoichiometries, thus indicating preferable interaction of enrofloxacin with single-strand regions of DNA. The binding
of other fluoroquinolones (lomefloxacin, ciprofloxacin, norfloxacin, danofloxacin and sarafloxacin) with d-DNA is very similar
to that of enrofloxacin: the binding constants are in the range from 0.94 × 105 to 2.40 × 105 M−1, and the stoichiometries range from 4.1 to 6.9 fluoroquinolone molecules per 100 DNA bases. The binding properties were quantitatively
the same for extraction of fluoroquinolones from model aqueous solutions and from liquid food (milk). The results indicate
the efficiency of DNA for selective extraction of fluoroquinolones from real samples for further analysis. This selective
binding also allows us to consider DNA as a natural receptor for development of analytical techniques for fluoroquinolones. 相似文献
3.
E. S. Chukhrai O. S. Pilipenko R. A. Ovsyannikov L. F. Atyaksheva E. E. Knyazeva I. I. Ivanova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(11):1986-1992
It is shown by the kinetic analysis of lysozyme and β-galactosidase adsorption on silochrome, silica gel, and mesoporous silica
that the adsorption follows a two-stage scheme, including reversible pre-adsorption and the irreversible binding of dimmers.
The corresponding rate constants of adsorption, desorption, and dimerization were calculated. It was found that β-galoctosidase
adsorbed on silica gel and mesoporous silica retained ∼20% of its activity, while β-galoctosidase adsorbed on silochrome retained
more than 30% of its activity. 相似文献
4.
L. N. Vakhitova S. V. Zhil’tsova A. V. Skrypka N. G. Razumova N. A. Taran V. A. Savelova A. F. Popov 《Theoretical and Experimental Chemistry》2006,42(5):287-294
The kinetics and mechanism of the catalysis by ammonium hydrogen carbonate oxidation of methyl phenyl sulfide with hydrogen
peroxide has been investigated. Using the classical pseudo-phase model of micellar catalysis, the basic parameters of the
catalytic process have been determined: the binding constants of H2O2, the HCO
4
−
anion, and the substrate to the surface of the micelles, and also the second order rate constants for the oxidation of methyl
phenyl sulfide in the micellar phase.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 281–287, September–October, 2006. 相似文献
5.
A New Approach for Titration Calorimetric Data Analysis on the Binding of Magnesium Ion with Myelin Basic Protein 总被引:1,自引:0,他引:1
G. Rezaei Behbehani A. A. Saboury A. Fallah Baghery 《Journal of solution chemistry》2008,37(8):1127-1135
The interaction of the myelin basic protein (MBP) from the bovine central nervous system with divalent magnesium ion was studied
by isothermal titration calorimetry at 27 °C in aqueous solution. A simple rapid method for determination of the dissociation
binding constants for Mg2+-MBP interaction was introduced using the isothermal titration calometric data. The binding isotherm for Mg2+-MBP interaction is easily obtained by carrying out a titration calorimetric experiment using only one set of concentrations
of MBP. There are two identical independent intrinsic association constants equal to 0.021 μmol⋅L−1 in the first- and second-binding sites, respectively. 相似文献
6.
The effects of temperature and common ions on binding of puerarin to bovine serum albumin (BSA) are investigated. The binding
constants (K
a) between puerarin and BSA are 1.13×104 L⋅mol−1 (20 °C) and 1.54×104 L⋅mol−1 (30 °C), and the number of binding sites (n) is (0.95±0.02). However, at a higher temperature (40 °C) the stability of the puerarin–BSA system decreases, which results
in a lower binding constant (1.58×103 L⋅mol−1) and number of binding sites (n=0.73) of the puerarin–BSA system. However, the presence of Cu2+ and Fe3+ ions increases the binding constants and the number of binding sites in the puerarin–BSA complex. 相似文献
7.
Xin Liu Xiaoqing Chen Jianbo Xiao Jinyao Zhao Feipeng Jiao Xinyu Jiang 《Journal of solution chemistry》2010,39(4):533-542
In this paper, the effect of hydrogenation on ring C of flavonols on the affinity for bovine serum albumin was investigated.
Two differently substituted B-ring hydroxylation flavonols (myricetin and quercetin) and their dihydrides (dihydromyricetin
and dihydroquercetin) were used to study their affinities for BSA by quenching the intrinsic BSA fluorescence in solution.
From the spectra, the bimolecular quenching constants, the binding constants, the number of binding sites and the binding
distances were calculated. The hydroxylation on ring B and hydrogenation on ring C of flavonols significantly affected the
binding/quenching process; in general, the hydroxylation increased the affinity and the hydrogenation decreased the affinity.
For myricetin and quercetin, the binding constants (K
a) for BSA were 1.84×108 L⋅mol−1 and 3.83×107 L⋅mol−1. For dihydromyricetin, the binding constant was 1.36×104 L⋅mol−1, while dihydroquercetin hardly quenched the BSA intrinsic fluorescence. These results showed that hydrogen bonding and conjugative
effects may play an important role in binding of flavonols to BSA. These results also showed that the properties of flavonols
are related to their chemical structure. 相似文献
8.
Íñigo X. García-Zubiri Gustavo González-Gaitano José Ramón Isasi 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):265-270
Automated semi-rigid docking has been explored as an alternative approach for the theoretical study of the inclusion complexes
with cyclodextrins. To this purpose we have chosen as a model for the binding to βCD some naphthalene derivatives (naphthalene,
2-ethylnaphthalene, 2-acetylnaphthalene, 1-naphthyl acetate, 2-naphthyl acetate and 1-naphthol). For comparison purposes,
the binding constants in water and the associated thermodynamic parameters have been obtained under the same experimental
conditions by steady-state fluorescence spectroscopy. The calculations of the automated docking regarding the topology of
the guest inside the cavity produce a cluster of structures that qualitatively agrees with fluorescence results and literature
data. However, the predicted values of the free energy of binding are lower than the experimental ones by ca. −10 kJ mol−1, and very close to the experimental enthalpy of binding deduced from the temperature dependence of the association constants.
The differences are ascribed mainly to the assumption of rigidity of the CD into the auto-docking scheme. 相似文献
9.
M. Khorasani-Motlagh M. Noroozifar M. Zabihi 《Russian Journal of Inorganic Chemistry》2010,55(8):1266-1270
The binding of bis-nitrogen ligands, 4,4′-bipyridine and pyrazine, to Zn(OEP), where OEP is octaethylporphyrin, has been characterized
by electronic spectroscopy. The solvent effect and temperature on the binding constants have been studied. Also, based on
variable temperature experiment, thermodynamic data for ligand binding to porphyrin have been reported. It is estimated that
interaction between porphyrin and 4,4′-bipyridine and pyrazine is exothermic and has energy of −45 ± 1.5 kJ mol−1 and −31 ± 1.7 kJ mol−1, respectively. 相似文献
10.
E. Gelagutashvili 《Journal of Thermal Analysis and Calorimetry》2006,85(2):491-494
Equilibrium
dialysis and atomic absorption analysis were used to obtain adsorption isotherms
and determine the stoichiometric binding constants of Cu(II) and Cd(II) ions
to DNA from Spirulina platensis in solutions.
The stoichiometric constants of Cu(II) and Cd(II) ions with DNA from S. platensis in 3 mM NaCI are 15.56⋅104
and 14.40⋅104, respectively.
Effect
of ionic strength and DNA GC content on binding constants of Cu(II)- and Cd(II)-DNA
complexes were studied out. It was showed that the binding constants of Cu(II)-
and Cd(II)-DNA complexes decrease with increase of ionic strength. The empirical
dependences of logK on the GC content has been derived for Cd(II)- and Cu(II)-DNA
complexes. 相似文献
11.
A kinetic study of the tumor-associated galactopyranosyl-(1→3)-2-acetamido-2-deoxy-α-d-galactopyranoside (T-antigen) with lectin peanut agglutinin is described. The disaccharide antigen was synthesized by chemical
methods and was functionalized suitably for immobilization onto a carboxy-methylated sensor chip. The ligand immobilized surface
was allowed interaction with the lectin peanut agglutinin, which acted as the analyte and the interaction was studied by the
surface plasmon resonance method. The ligand—lectin interaction was characterized by the kinetic on-off rates and a bivalent
analyte binding model was found to describe the observed kinetic constants. It was identified that the antigen-lectin interaction
had a faster association rate constant (k
a1) and a slower dissociation rate constant (k
d1) in the initial binding step. The subsequent binding step showed much reduced kinetic rates. The antigen-lectin interaction
was compared with the kinetic rates of the interaction of a galactopyranosyl-(1→4)-β-d-galactopyranoside derivative and a mannopyranoside derivative with the lectin. 相似文献
12.
Jing-yao Liu Ze-sheng Li Zhen-wen Dai Xu-ri Huang Chia-chung Sun 《Theoretical chemistry accounts》2002,108(3):179-186
The hydrogen-abstraction reaction C2H5F+O → C2H4F+OH has been studied by a dual-level direct dynamics method. For the reaction, three reaction channels, one for α-abstraction
and two for β-abstraction, have been identified. The potential-energy surface information is obtained at the MP2(full)/6-311G(d,p)
and PMP2(full)/6-311G(3df,3pd) (single-point) levels. By canonical variational transition-state theory, rate constants for
each reaction channel are calculated with a small-curvature tunneling correction. The total rate constant is calculated from
the sum of the individual rate constants and the temperature dependence of the branching ratios is obtained over a wide range
of temperatures from 300 to 5,000 K. The agreement of the rate constants with experiment is good in the experimental temperature
range from 1,000 to 1,250 K. The calculated results indicate that at low temperatures α-abstraction is most likely to be the
major reaction channel, while β-abstraction channels will significantly contribute to the whole reaction rate as the temperature
increases.
Received: 23 January 2002 / Accepted: 23 June 2002 / Published online: 20 September 2002 相似文献
13.
Carolina Jullian Muriel Alfaro Gerald Zapata-Torres Claudio Olea-Azar 《Journal of solution chemistry》2010,39(8):1168-1177
The formation of the complexes of galangin (GAL) with native β-cyclodextrin (βCD), and with its substituted counterparts such
as dimethyl-βCD (DMβCD) and hydroxypropyl-βCD (HPβCD), was studied by fluorescence spectra in aqueous medium. The binding
association constants (K
a) of the complexes were determined at different temperatures. The formation constants obtained have the following trend upon
complex formation at the three temperatures studied: HPβCD > DMβCD > βCD. The thermodynamic data for the inclusion of GAL
in DMβCD and HPβCD indicated that is mainly enthalpy driven whereas for βCD it is an entropy-driven process. 相似文献
14.
Hassan NM Murimboh JD Sekaly AL Mandal R Chakrabarti CL Grégoire DC 《Analytical and bioanalytical chemistry》2006,384(7-8):1558-1566
Kinetic speciation of nickel, aluminium, and iron in fresh water has been investigated by cascade ultrafiltration followed by competing ligand exchange of the ultrafiltered fractions. Graphite furnace atomic absorption spectrometry was used to measure the kinetics of metal complex dissociation. Dissolved metal species were fractionated by cascade ultrafiltration. Metal speciation in each ultrafiltered fraction was then characterized as free metal ions, “labile” metal complexes (with dissociation rate constants ≥10−3 s−1), “slowly labile” metal complexes (with dissociation rate constants >10−6 s−1), and “inert” metal complexes (with dissociation rate constants <10−6 s−1). The experimental results were compared with the predictions of a computer-based equilibrium speciation model, the Windermere humic aqueous model (WHAM) V. Cascade ultrafiltration coupled with kinetic speciation of the metal species in each molecular weight cut-off (MWCO) fraction provided a more comprehensive picture and insight into the physical and the chemical characteristics of the metal species than either ultrafiltration or measurement of dissociation kinetics alone. 相似文献
15.
Yan Shi Xiancheng Zhan Lie Ma Linli Li Chengrong Li 《Frontiers of Chemistry in China》2007,2(2):140-145
An evaluation method for the capacity of antioxidants to protect drugs against oxidation is presented. As a new viewpoint,
to determine the priority of the competitive oxidations between the antioxidant and the protected drug, and to compare the
drug-protection capacity of antioxidants, it is important to determine their oxidation rate constants using chemical kinetics
instead of standard oxidation (or reduction) potentials. Sodium sulfite, sodium bisulfite and sodium pyrosulfite were used
as models for the determination of oxidation reaction rate constants in aqueous solutions. In the experiments, sufficient
air was continually infused into the solution to keep the concentration of dissolved oxygen constant. The residual concentrations
of the antioxidants were determined by iodimetry, and the concentration of dissolved oxygen by oxygen electrode. The data
were fitted by linear regressions to obtain the reaction rate constants. It was found that the degradation of sodium sulfite,
sodium bisulfite or sodium pyrosulfite obeyed pseudo zero-order kinetics in the buffer solutions. Because of the ionization
equilibrium, these three antioxidants have the same ion form in solutions at a definite pH value and therefore their apparent
rate constants were essentially the same. The average apparent rate constants of the three antioxidants at 25°C are (1.34
± 0.03) × 10−3 at pH 6.8, (1.20 ± 0.02) × 10−3 at pH 4.0 and (6.58 ± 0.02) × 10−3 mol·L−1·h−1 at pH 9.2, respectively.
Translated from Acta Chimica Sinica, 2006, 64(6): 496–500 (in Chinese) 相似文献
16.
The rate constants of the reactions of1O2 with 3,5,7,3′,4′-pentamethoxy-, 3-hydroxy-5,7,3′,4′-tetramethoxy-, and 5-hydroxy-3,7,3′,4′-tetramethoxyflavones in benzene
were measured. The methylation of quercetin was found to result in an increase in the rate due to the enhancement of the electron-donating
activity of the molecules. 相似文献
17.
U. S. Mote S. L. Bhattar S. R. Patil G. B. Kolekar 《Journal of solution chemistry》2009,38(5):619-628
The interaction between fluorescein and felodipine (FLD) was investigated by the spectrofluorometric method. The fluorescence
of FLD was quenched by fluorescein and quenching is in accordance with the Stern-Volmer relation. The binding constants of
fluorescein with FLD were obtained at different temperatures. The binding constant and number of binding sites at different
temperatures were calculated yielding the corresponding thermodynamic parameters ΔS, ΔH and ΔG. The distance r between the donor (FLD) and acceptor (fluorescein) molecules was obtained according to the fluorescence resonance energy
transfer. The optimum conditions for the fluorometric determination of fluorescein were studied and the quenching method was
successfully applied to estimate the fluorescein concentration of the pharmaceutical sample directly. 相似文献
18.
T. P. Elango V. Ramakrishnan S. Vancheesan J. C. Kuriacose 《Journal of Chemical Sciences》1984,93(1):47-52
Rate constants for the reaction of carbonate radical with aniline and some parasubstituted anilines have been determined by
the flash photolysis technique. Using σ+ para values the rate constants at pH 8.5 correlate very well with the Hammett equation yielding ρ= − 1. The carbonate radical oxidises aniline giving the anilino radical. The products so formed have been identified through
studies under conditions of continuous irradiation. 相似文献
19.
E. S. Chukhrai L. F. Atyaksheva O. S. Pilipenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(5):890-896
The adsorption isotherms of hemoglobin, peroxidase, and β-galactosidase on silochrome and mesoporous and biporous silicas
were comparatively studied. Adsorption developed in two stages, including fast “reversible” protein adsorption (equilibrium
was reached in t ≤ 1–2 h) and a “slow stage” of irreversible binding in t ≫ 24 h (multipoint adsorption). The corresponding equilibrium constants were determined. The mechanism of unlimited linear
association of peroxidase in the adsorption layer on the surface of silochrome was established. 相似文献
20.
Aureliano Antunes CS Bietti M Ercolani G Lanzalunga O Salamone M 《The Journal of organic chemistry》2005,70(10):3884-3891
[reaction: see text] A product and time-resolved kinetic study of the effect of ring substitution on the reactivity of 1,1-diarylalkoxyl radicals has been carried out. The radicals undergo an O-neophyl shift to give the isomeric 1-aryl-1-aryloxyalkyl radicals from which the corresponding aromatic ketones are formed. The rearrangement rate constants are influenced by ring substitution, increasing in the presence of electron-withdrawing substituents and decreasing in the presence of electron-donating ones. From the results of product and kinetic studies, the following migratory aptitudes have been obtained: 4-trifluoromethylphenyl > phenyl approximately = 4-methylphenyl > 4-methoxyphenyl. Excellent Hammett-type correlations between the sigma+ substituent constants and both the visible absorption band maxima and the rearrangement rate constants have been obtained. The experimental results indicate that the rearrangement is governed by electronic effects in the starting 1,1-diarylalkoxyl radicals, whereas the stability of the rearranged carbon-centered radical plays a minor role, in line with a reactant-like transition state, strongly supporting the hypothesis that the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals proceeds through a concerted mechanism. 相似文献