Fluorescent Proteins - Quantifiying calcium
Quantification of fluorescent proteins can be done by using the same rules described for quantification of fluorescent dyes. Cameleons are usually employed as ratiometric indicators while other fluorescent proteins are used as non-ratiometric indicators.
In the case of cameleons, the ratio between the donor excitation wavelength and the acceptor emission wavelength allows an increase in the signal to noise ratio and also has the advantages of ratiometric methods. There is just an important difference between dyes and proteins: Hill coefficient has to be considered in the case of fluorescent proteins that present a cooperative mechanism.