Fluorescence equilibrium studies

Equilibrium Studies of Receptor-Ligand Interactions Monitored by Fluorescence.141... 

An alternative mechanism for the formation of a two hosts-two guests complex has been suggested. From equilibrium studies of the concentration-dependence of the absorption spectra and excimer fluorescence intensities of naphthalene in the presence of beta cyclodextrin, Hamai ° concluded that the excimer fluorescence is due to a two hosts-two guests complex, formed by the association of two 1 1 beta cyclodextrin-naphthalene complexes. Thus, the mechanism can be described as follows. 

Figure 9.30. (a) Adsorption isotherm of sodium dodecyl sulfate (SDS) on alumina at pH 6.5 in 0.1 M NaCl. (b) Zeta potential of alumina as a function of equilibrium concentration of SDS (designation of regions based on isotherm shape). (From Chandar et al., 1987 based on the data of Somasundaran and Fuerstenau, 1966.) Chandar et al. (1987) have shown with the aid of fluorescent probe studies that in region II and above adsorption occurs through the formation of surfactant aggregates of limited size. 

Folding Equilibrium Studies. E. coli RTEM p-lactamase is a monomeric protein. Its amino acid sequence has been determined (79). It has one disulfide bond between the residues Cys S and Cys. The presence of four tyrosines and four tryptophans allows the use of spectroscopic method for the conformational characterization of the enzyme. In this study, the effect of denaturants on the unfolding of p-lactamase was determined from activity measurements, difference spectroscopy and fluorescence intensity measurements. 

Li Y, Edsall J, R, Jagtap PG, Kingston DGI, Bane S (2000) Equilibrium Studies of a Fluorescent Paclitaxel Derivative Binding to Microtubules. Biochemistry 39 616... 

Up to the present the principal interest in heteroaromatic tautomeric systems has been the determination of the position of equilibrium, although methods for studying fast proton-transfer reactions (e.g., fluorescence spectroscopy and proton resonance ) are now becoming available, and more interest is being shown in reactions of this type (see, e.g., references 21 and 22 and the references therein). Thus, the reactions of the imidazolium cation and imidazole with hydroxyl and hydrogen ions, respectively, have recently been demonstrated to be diffusion controlled. ... 

Visser, A. J. W. G., and Lee, J. (1980). Lumazine protein from the bioluminescent bacterium Photobacterium phosphoreum. A fluorescence study of the protein-ligand equilibrium. Biochemistry 19 4366-4372. 

In 1999, the Klemperer group published experimental results from a dispersed fluorescence study of the linear and T-shaped Ar l2(X, v = 0) conformers to obtain information about the X- and B-state potentials of the complex and to gain insight into the photodissociation dynamics in the B electronic state [65]. In carrying out their analysis, they assumed that the linear and T-shaped conformers existed in a thermodynamic equilibrium, with the abundance of the linear conformer being three times that of the T-shaped conformer. In an effort to test the validity of the thermodynamic hypothesis Bastida, et al. [66], performed a... 

In summary, the advantage of using fluorescence correlation spectroscopy is that very small sample volumes can be employed and the system is studied at equilibrium without the need to perturb the chemical equilibrium. The disadvantages of the technique are difficulties in differentiating between artifactual signals and relaxations related to chemical phenomena and the development of suitable models for fitting the correlation curves. 

Nuclear magnetic resonance (NMR) experiments are used to study the exchange kinetics of chemical systems in equilibrium.28,68,69 As is the case for fluorescence correlation spectroscopy no perturbation of the chemical system in equilibrium is required to obtain kinetic information from NMR experiments. However, NMR is not very sensitive to concentration changes. 

Flash photolysis studies with absorption or delayed fluorescence detection were performed to compare the binding of ground and excited state guests with DNA.113,136 The triplet lifetimes for 5 and 6 were shown to be lengthened in the presence of DNA.136 The decays were mono-exponential with the exception of the high excitation flux conditions where the triplet-triplet annihilation process, a bimo-lecular reaction, contributed to the decay. The residence time for the excited guest was estimated to be shorter than for the ground state, but no precise values for the rate constants were reported. However, the estimated equilibrium constants for the... 

In order to study the molecular dynamics of the outer segments of a dendrimer, one pyrene moiety was selectively and covalently attached to one dendron of poly(aryl ester) dendrimers by Adams (in total three pyrene molecules per dendrimer) [24]. The fluorescence decay of pyrene in the THF solution of the labeled dendrimers provided details of the pyrene excimer formation, such as the excimer formation rate, the excimer decomposition rate constant and the equilibrium constant of the excimer formation. These parameters were utilized to evaluate the diffusional mobility of the dendrimer branches. 

Fluorescence polarization is also well suited to equilibrium binding studies when the free and bound species involved in the equilibrium have different rotational rates (Scheme 5.1). Most molecular interactions can be analyzed by this method. It should be emphasized that, in contrast to other methods using tracers, fluorescence polarization provides a direct measurement of the ratio of bound and free tracer without prior physical separation of these species. Moreover, measure-... 

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