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Quenching is the basis for Förster resonance energy transfer (FRET) assays. [5] [6] [7] Quenching and dequenching upon interaction with a specific molecular biological target is the basis for activatable optical contrast agents for molecular imaging. [8] [9] Many dyes undergo self-quenching, which can decrease the brightness of protein-dye ...
The Dexter energy transfer rate, , is indicated by the formula: = ′ [] where is the separation of the donor from the acceptor, is the sum of the Van der Waals radii of the donor and the acceptor, and ′ is the normalized spectral overlap integral, where normalized means that both emission intensity and extinction coefficient have been adjusted to unit area.
The Stern–Volmer relationship, named after Otto Stern and Max Volmer, [1] allows the kinetics of a photophysical intermolecular deactivation process to be explored. Processes such as fluorescence and phosphorescence are examples of intramolecular deactivation ( quenching ) processes.
Furthermore, tryptophan fluorescence is strongly influenced by the proximity of other residues (i.e., nearby protonated groups such as Asp or Glu can cause quenching of Trp fluorescence). Also, energy transfer between tryptophan and the other fluorescent amino acids is possible, which would affect the analysis, especially in cases where the ...
is the fluorescence in the absence of halide F {\displaystyle F} is the fluorescence in the presence of halide K {\displaystyle K} is the Stern–Volmer quenching constant, which depends on the chloride concentration, [ C l − ] {\displaystyle [Cl^{-}]} . in a linear manner.
The efficiency of photochemical quenching (which is a proxy of the efficiency of PSII) can be estimated by comparing to the steady yield of fluorescence in the light and the yield of fluorescence in the absence of photosynthetic light . The efficiency of non-photochemical quenching is altered by various internal and external factors.
Instead of a mechanical stopping system, the reaction is halted by quenching, where the products are immediately stopped by freezing, chemical denaturation, or exposure to a denaturing light source. Similar to the continuous-flow method, the time between mixing and quenching can be adjusted by varying the length of the reaction tube.
This results in fluorescence quenching (active electron transfer), and the emission from the chemosensor is 'switched off,' for both mechanisms in the absence of the analytes. However, upon forming a host–guest complex between the analyte and receptor, the communication pathway is broken and the fluorescence emission from the fluorophores is ...