Analysis of fluorescence quenching of new indole derivative by aniline using Stern–Volmer plots

The steady-state tryptophan fluorescence and time-resolved tryptophan fluorescence of Escherichia coli thioredoxin, calf thymus thioredoxin, and yeast thioredoxin have been studied. In all proteins, the tryptophan residues undergo strong static and dynamic quenching, probably due to charge-transfer interactions with the nearby sulfur atoms of the active cysteines. The use of a high-resolution photon counting instrument, with a time response of 60 ps full width at half-maximum, allowed the detection of fluorescence lifetimes ranging from a few tens of picoseconds to 10 ns. The data were analyzed both by classical nonlinear least squares and by a new method of entropy maximization (MEM) for the recovery of lifetime distributions. Simulations representative of the experimental data were used to test the MEM analysis. Strong support was obtained in this way for a small number of averaged discrete species in the fluorescence decays. Wavelength studies show that each of these components spreads over closely spaced excited states, while the temperature studies indicate that they do not exchange significantly on the nanosecond time scale. The oxidized form of thioredoxin is characterized by a high content of a very short lifetime below 70 ps, the amplitude of which is sharply decreased upon reduction. On the other hand, the fluorescence anisotropy decays indicate that reduction causes an increase of the very fast tryptophan rotations in an otherwise relatively rigid structure. While the calf thymus and E. coli proteins have mostly similar dynamical fluorescence properties, the yeast thioredoxin differs in many respects.

Picosecond tryptophan fluorescence of thioredoxin: evidence for discrete species in slow exchange.

Role of solvent polarity on the fluorescence quenching of newly synthesized 7,8-benzo-4-azidomethyl coumarin by aniline in benzene–acetonitrile mixtures

The quenching of fluorescence of 2-(4′- t -butylphenyl)-5-(4′′-biphenylyl)-1,3,4-oxadiazole (BPBD) has been studied by aniline in different solvent mixtures of benzene and acetonitrile at room temperature. The quenching is found to be appreciable and a positive deviation from linearity was observed in the Stern–Volmer plot in all the solvent mixtures. Various rate parameters for the quenching process have been determined by sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern–Volmer plot is due to both static and dynamic processes. The dependence of Stern–Volmer constant on dielectric constant of the solvent mixture indicates the possibility of different solvent molecule composition around the fluorescent from that of the bulk.

Fluorescence quenching of BPBD by aniline in benzene–acetonitrile mixtures

Exploring the mechanism of fluorescence quenching in two biologically active boronic acid derivatives using Stern-Volmer kinetics

Fluorescence quenching of carbazole and indole by ethylenetrithiocarbonate

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Fluorescence quenching of carbazole and indole by ethylenetrithiocarbonate