Fluorescent probes quenching

Kolubayev T, Geacintov N E, Paillotin G and Breton J 1985 Domain sizes in chloroplasts and chlorophyll-protein complexes probed by fluorescence yield quenching induced by singlet-triplet exciton annihilation Biochimica Biophys. Acta 808 66-76... 

The silver clusters can be applied as fluorescent probes to retrieve information about the chemical environment. There are reported three classes of sensors based on silver clusters. First, we discuss silver cluster sensors of which the fluorescence quenches in the presence of the analyte. Second, we discuss a sensor in which fluorescent clusters are formed only in presence of the analyte. Finally, we discuss the shift in the absorption and fluorescence bands of silver clusters while sensing the chemical environment. 

Let us consider a fluorescent probe and a quencher that are soluble only in the micellar pseudo-phase. If the quenching is static, fluorescence is observed only from micelles devoid of quenchers. Assuming a Poissonian distribution of the quencher molecules, the probability that a micelle contains no quencher is given by Eq. (4.22), so that the relationship between the fluorescence intensity and the mean occupancy number < > is... 

Method II Dynamic quenching by totally micellized immobile quenchers It is assumed that the probability of quenching of a fluorescent probe in a given micelle is proportional to the number of quenchers residing in this micelle. The rate constant for de-excitation of a probe in a micelle containing n quencher molecules is given by... 

The development of fluorescent probes for anion recognition has been very limited so far in comparison with those for cations. Most of the presently available methods of detection of anions based on fluorescence involve quenching, redox reactions, substitution reactions, ternary complex formation(15) and thus cannot be considered as recognition methods. For instance, the fluorescent sensors that are used for the determination of chloride anions in living cells are based on collisional quenching of a dye by halide ions 6-methoxy-iV-(sulfopropyl)quinoliniuni and... 

The labeling can also be done by fluorescence lifetime differences, e.g., introduced by quenching pathways connected with different surroundings. This can be used for lifetime imaging methods (Chapter 1, this volume) or for distinguishing complexes of one and the same fluorescence label with, e.g., different DNA-bases. In this case, the fluorescence label is not only a label but incorporates a function which senses the environment and can therefore be regarded as a sensing fluorescence probe. 

Fluorescent Probes with an Efficient Intramolecular Fluorescence Quenching Process in the Base Form Possibly Related to the Formation of a Nonemissive TICT State... 

In studies where either intrinsic fluorescence or quenching is a confounding variable, the botanical product should be examined in an assay using a chromatographic separation step with a representative probe substance for the isozyme (29) being examined. 

Figure 11 [76-79]. In this system, Pe or DPA in the droplet acts as a fluorescence probe for the interfacial ET. Namely, fluorescence of Pe or DPA in the droplet is quenched by FeCp-X, but not by FeCp-X+ produced by the ET reaction. Therefore, the time course of the FeCp-X concentration in the oil droplet ([FeCp-X]0) during electrolysis of Fe(II) in water can be determined by that of the fluorescence intensity of the fluorescer (/F). Although fluorescence quenching by Fe(II) or Fe(III) is also expected to take place at the droplet/water interface, such a contribution is neglected compared to the quenching by FeCp-X in the droplet interior, owing to the short diffusion length of the excited singlet state Pe or DPA.

Fluorescent compounds are sensitive to changes in their chemical environment. Alterations in media pH, buffer components, solvent polarity, or dissolved oxygen can affect and quench the quantum yield of a fluorescent probe (Bright, 1988). The presence of absorbing components in solution that absorb light at or near the excitation wavelength of the fluorophore will have the effect of decreasing luminescence. In addition, noncovalent interactions of the probe with other components in solution can inhibit rotational freedom and quench fluorescence. 

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