Patterson, G. H. and Lippincott-Schwartz, J.
A photoactivatable GFP for selective photolabeling of proteins and cells.  Science 297: 1873-1877 (2002).

We report a photoactivatable variant of the Aequorea Victoria green fluorescent protein (GFP) that, after intense irradiation with 413-nanometer light, increases fluorescence 100 times when excited by 488-nanometer light and remains stable for days under aerobic conditions. These characteristics offer a new tool for exploring intracellular protein dynamics by tracking photoactivated molecules that are the only visible GFPs in the cell. Here, we use the photoactivatable GFP both as a free protein to measure protein diffusion across the nuclear envelope and as a chimera with a lysosomal membrane protein to demonstrate rapid interlysosomal membrane exchange.