Kinetics fluorescence quenching

Kinetic Fluorescence-Quenching Detection Assay for Allele Frequency Estimation... 

Pajkossy and co-workers have published an interesting series of p>apers devoted to the electrochemistry on fractal surfaces (Nyikos Pajkossy, 1986 Pajkossy Nyikos, 1989a Pajkossy Nyikos, 1989b Nyikos et al., 1990 Borosy et al., 1991). Diffusion to rough surfaces plays an important role in diverse fields, e.g., in catalysis, enzyme kinetics, fluorescence quenching and spin relaxation. Nyikos and Pajkossy have shown that, as a consequence of fractal electrode surface, the diffusion current is dependent on time as i X t, where Dy is the fractal dimension (Nyikos Pajkossy, 1986). For a smooth, two-... 

Equations (4-5) and (4-7) are alternative expressions for the estimation of the diffusion-limited rate constant, but these equations are not equivalent, because Eq. (4-7) includes the assumption that the Stokes-Einstein equation is applicable. Olea and Thomas" measured the kinetics of quenching of pyrene fluorescence in several solvents and also measured diffusion coefficients. The diffusion coefficients did not vary as t) [as predicted by Eq. (4-6)], but roughly as Tf. Thus Eq. (4-7) is not valid, in this system, whereas Eq. (4-5), used with the experimentally measured diffusion coefficients, gave reasonable agreement with measured rate constants. 

FIG. 12 Simulation of fluorescent decays for dye species located in the aqueous phase following laser pulses in TIR from the water-DCE interface according to Eq. (38). A fast rate constant of excited state decay (10 s ) was assumed in (a). The results showed no difference between infinitely fast or slow kinetics of quenching. On the other hand, a much slower rate of decay can be observed for other sensitizers like Eu and porphyrin species. Under these conditions, heterogeneous quenching associated with the species Q can be readily observed as depicted in (b). (Reprinted with permission from Ref 127. Copyright 1997 American Chemical Society.)... 

Based on analogies we have cited, the kinetic scheme proposed for heavy-atom fluorescence quenching is reasonable and would predict the following relationship for fluorescence quenching ... 

Fluorescence quenching studies of these alkylated FBAs in aqueous solution were carried out using spectroscopic techniques. For the higher members of each series, plots of fluorescence quantum yield against agent concentration showed a sharp decrease in fluorescence intensity at a specific concentration, in contrast to the smoothly decreasing curve characteristic of the lower alkyl or unsubstituted FBAs. The kinetics of fluorescence... 

Rehm D, Weller A (1970) Kinetics of fluorescence quenching by electron and H-atom transfer. Isr J Chem 8 259... 

Homotransfer does not cause additional de-excitation of the donor molecules, i.e. does not result in fluorescence quenching. In fact, the probability of de-excitation of a donor molecule does not depend on the fact that this molecule was initially excited by absorption of a photon or by transfer of excitation from another donor molecule. Therefore, the fluorescence decay of a population of donor molecules is not perturbed by possible excitation transport among donors. Because the transition dipole moments of the molecules are not parallel (except in very rare cases), the polarization of the emitted fluorescence is affected by homotransfer and information on the kinetics of excitation transport is provided by the decay of emission anisotropy. 

Compound 138 is a remarkably efficient quencher of methylene blue fluorescence quenching occurs presumably by a redox process. It is necessary to consider physical quenching as well as trapping in a kinetic treatment of O2 reactions, however, quenching of O2 by 138 does... 

It is commonly assumed, therefore, that solvent reorganization will dominate electron transfer kinetics and that the reorganization energy in the same medium will be constant within a series of closely related redox partners. With a value of 2.4 kcal/mole for solvent reorganization (as obtained by Rehm and Weller (7) for fluorescence quenching of a series of arenes by substituted anilines in a polar medium) the curve shown in Fig. 2 is obtained. It is clear that substantial solvent-dependent barrier to electron exchange can be encountered. 

In the last two cases, we would still expect a behavior of the short-wavelength FB band similar to that of DMABN There, the kBA channel toward the TICT state leads to efficient fluorescence quenching of FB. This can be seen directly in the low-temperature range, for example, in Fig. 2.1 (Section II.A), below 180 K, where the quantum yield of FB fluorescence increases upon cooling because the horizontal radiationless transition kBA is slowed down. The simplified Kinetic Scheme II, also valid for any other monomolecular quenching process, describes this... 

Lin, C.-E, Houng, L.-M. and Lo, K.S. (1994) Kinetics of copper complexation with dissolved organic matter using stopped-flow fluorescence quenching. Toxicol. Environ. 

If one studies only the fluorescence quenching by irreversible bimolecular ionization (3.52), there is seldom any need to trace the fate of the charged products. On the contrary, those who are interested in photoinduced geminate recombination (3.188) rarely care about the kinetics of ionization, its quenching radius, and all the rest studied in Section III. All that they need to obtain the charge separation yield is the initial ion distribution mo(r), prepared by photoionization. However, the latter is scarcely so simple as in Eq. (3.201), which is usually favored. Even so, the initial separation ro is not a fitting parameter but the characteristic interion distance, which is dependent on the precursor reaction of photoionization. 

The initial charge distributions, which were recognized as very important, were analyzed in more detail in a number of works [32]. The analysis was extended to multichannel ionization [179], and the role of the excitation lifetime was specified [25]. A few articles devoted to them were published by Murata and Tachiya [26,27]. Earlier these authors studied experimentally the non-stationary kinetics of fluorescence quenching, which was fitted numerically... 

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