October 4, 2005 - The German Max Planck Society announced last Thursday that they had isolated the molecular mechanism behind switchable fluorescent proteins, which could potentially lead to using the proteins in crystalline form as optical storage devices. The results are a joint effort between Goettingen photobiophysicists, X-Ray crystallographers, computer-biophysicists, and cell biologists.
The protein asFP595, found in a species of coral native to the North Atlantic and the Mediterranean, generally makes the snakelocks anemone Anemonia sulcata green, but a lot of sunlight causes the tips of the anemone tendrils to emit red light. If another light is applied to the anemone tissue, the protein can switch back and forth from a fluorescent to a non-fluorescent state. Scientists have known that such proteins exist for some time, but what happened on a molecular level to cause this switch was previously unknown.
By cultivating bacteria that produce the protein and building crystals that contain the protein as well, researches used computer simulations and X-Ray analysis to determine that the photosensitive part of the protein does a “hula twist” when it absorbs the light. This is a type of cis-trans isomerisation that rearranges the spatial configuration of a chemical bond between three atoms, causing other parts of the protein to shift very slightly on its axis. This moves the protein a third of a billionth of a meter, but the tiny motion is enough—while geometric isomers have the same chemical bond structure, enzymes are sensitive to the different spatial configurations, thus making this alteration an effective “molecular light switch.”
Protein crystals made from asFP595 would contain millions of these switches, making them potentially useful for optical data storage.
