does anyone know of a fluorescent protein that upon binding of a substrate its fluorescence is activated? i've been looking on this and perhaps my keywords are not the right ones. Thanks in advance
There are only 3 classes of fluorescent proteins proteins known I think. Two of them are relevant to your needs maybe.
The first are usually called 'fluorescent proteins'. These proteins are usually derived from the A victoria jellyfish. Its entirely passive in its fluorescence, but has been tuned to many levels of quantum yield and color.
There was a new sort of fluorescent protein cloned recently from japanese eels. It is activated by binding to bilirubin. Its so new that its not likely to be available, but there you go.
The third class would be the luciferases. They are luminescent, not fluorescent but in producing light involves binding from a cofactor called luciferase which is oxidized to produce their light. This is not really fluorescence since the electrical stimulation that causes light production is not from incident light, but since what you are looking for might not exist I wanted to remind you of the luciferases, which bind their redox substrates to activate. The luciferin molecule actually varies as there are several classes of luciferase. I think Flavin and NAD are the most common substrates.