No Need To FRET

F örster resonance energy transfer (FRET) is a method used to measure distances on a molecular scale. The problem with FRET, which works by transferring energy between fluorescent donor and acceptor molecules, is that it works only at distances shorter than about 10 nm. Scientists have long known that similar energy transfer occurs between fluorescent molecules and metals that quench those molecules’ fluorescence. This metal-induced energy transfer (MIET) shortens the fluorescence lifetime in a distance-dependent manner over distances as long as 200 nm, 20 times as long as FRET does. A team led by Alexey I. Chizhik and Jörg Enderlein of Georg August University, in Göttingen, Germany, has now used MIET to acquire images of live cells (Nat. Photonics. 2014, DOI: 10.1038/nphoton.2013.345). The researchers grew three types of cells on gold films, stained the cells with a membrane-specific fluorophore, and used MIET to construct a time-lapse series of images as the cells spread across the surface. Three-dimensional reconstructions of the basal cell membranes exhibited lateral resolution of 200 nm and axial resolution of 3 nm.