Quenching parameter

In addition, it is convenient to define the Bjerrum length parameter Lb = e z ) / f.eikTi (where is the universal dielectic constant) and the so-called quenching parameter, defined as g = EqTq/eiTi. 

Furthermore, the quenching of internal residues in proteins by ionic quenchers, although not strong, is quite detectable.(56) A double-quenching method was developed to separate fluorescence quenching parameters characteristic of solvent-exposed and buried fluorophores.(57) The method uses two types of quenchers simultaneously, one type penetrating and the other not penetrating into the protein matrix. 

B. Somogyi, S. Papp, A. Rosenberg, I. Seres, J. Matko, G. R. Welch, and P. Nagy, A doublequenching method for studying protein dynamics Separation of the fluorescence quenching parameters characteristic of solvent-exposed and solvent-masked fluorophores, Biochemistry 24, 6674-6679 (1985). 

The transient kinetics is not a unique source of information about the quenching parameters. Alternatively, the same parameters may be extracted from the stationary fluorescence data. In principle, the viscosity and concentration... 

Fig. 2. Polymer fraction vs. irradiation time for a 4-BCMU film, 1300 A thick. Data points are experimental, full curves are obtained for the energy transfer model for various quenching parameters k, = k To (from Ref. >)...

Table 30 Triplet quenching parameters of thiopyronine with N,N-dimethylated anilines (DMA)...

Fig. 9. Dependence of the Urbach slope parameter Eo (left scale) and photoluminescence quenching parameter To (right scale) on a-Si H layer thickness Lg. [From Abeles and Tiedje...

Fluorescence quenching parameters are estimated as an average of three individual experiments, and the uncertainty is the standard deviation. For the binding constant, the error for each fit was determined by using the standard error analysis method described by the equation cr, = where C is the diagonal element of... 

Figure 3 The effect of temperature on the rate of evolution, fluorescence quenching parameters qQ and qE, and the calculated intrinsic PSII yield, p for cells of Dunaliella illuminated at a PFD of 550maole quanta/nF/s...

In order to analyse the original fluorescence titration curve, all AS mx molecular parameters in equation 8b must be known. In the simplest case, all parameters could be the same, i.e. binding to each site would be characterized by the same quenching parameter, AS. In such a case, the dependence of AS,bs. as a function of Svj, would be strictly linear (dashed line in Rgure 2) and equation 8b would reduce to... 

One way of separating the fluorescence quenching parameters associated with external and internal fluorophores is to use a double-quenching method in which two quenchers are applied simultaneously. The first quencher is used to selectively quench the fluorescence emission of exposed fluorophores. On the other hand, the second quencher is used to quench the fluorescence emission of both surface and interior fluorophores non-selectively. 

Despite the usefulness of this approach, it is important to appreciate that there are many uncertainties from other contributions to quenching and from quenching parameters that are not well-determined. For example, the magnimde of outersphere quenching has not been determined for many types of Ln(lll) coordination complexes other than the type described above. Outersphere quenching is known to vary based on the charge and type of complex [16]. The efficiency of quenching is proportional to the distance of the quencher from the... 

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