Green Fluorescent Protein (GFP) is one of the most important proteins discovered, and it earned Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien the 2008 Nobel Prize in Chemistry. GFP is a fluorescent protein naturally found in the jellyfish Aequorea victoria. The scientists needed to collect enough protein to crystalize (100mg) and thus had to extract protein from 50,000 jellyfish.
Fluorescent means the electrons in the protein can be excited to a higher energy state than normal by ultraviolet light, 395 nm. The electrons then fall back down to their low energy state and release a photon at the 509 nm wavelength, or green! We use GFP as an easy way to track the production of protein. The more the solution fluoresces the more protein has been produced. The picture to the right is an Eppendorf tube containing a cell-free reaction producing GFP. The tube is resting on a UV table.