Applications of quenching
FLuorescene and phosphorescence quenching is often associated with a secondary process, such as electron transfer or energy transfer, that has useful applications. In any such process we can distinguish a donor, which is the luminescent molecule, and an acceptor, which receives the energy from light excitation following a transfer process of some kind. The fact that luminscence is quenched by the process can be useful in the laboratory since we can measure the extend to which energy or electrons are donated. In electron transfer we can use such systems to understand photosynthesis, artificial photosynthesis, charge injection at solar electrodes, electron transfer in molecule computing and many other such applications. In the field of energy transfer, there is fluorescent resonant energy transfer (FRET), which is widely used in cell biology and molecular biology as a method for determining the distance between two sites. The FRET efficiency is distance dependent. This if a donor and acceptor are close in distance the FRET signal can be observed (i.e. the change in color of fluorescence since eneryg is donated from one molecule to another). However, if the donor and accept move apart for any reason the FRET signal vanishes and one sees only the fluroescence of the donor. There are many situations where a donor/accept pair (a so-called FRET pair) can be attached to different sites on a protein to monitor conformational changes, unfolding, interaction with DNA or other proteins etc. One can also use FRET pairs on different molecules to monitor their binding in a cell. Energy transfer is also observed in the triplet-state manifold. We must carefully distinguish such triplet-triplet energy transfer from fluorescence, which is singlet-singlet energy transfer.
The laboratory protocol can be downloaded below:
The DHP lecture and notes can be downloaded as a PDF below
References
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