Live cell imaging: The 'green revolution' continues apace

The green fluorescent protein (GFP) from the jellyfish Aequoria victoria together with its blue- and yellow-shifted mutant variants, cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP), has revolutionized the way cell biologists follow the dynamics of proteins in living cells using modern imaging and spectroscopic techniques. CFP and YFP enable dual-color visualization of expressed proteins that fuse to these fluorescent tags. Furthermore, utilizing the phenomenon of Fluorescence Resonance Energy Transfer (FRET), vizualization of such proteins has enabled researchers to measure protein–protein interactions to determine intracellular Ca 2+ or cAMP concentrations, and to visualize dynamic phosphorylation events in live cells [ 1 ].