Metal-induced energy transfer for live cell nanoscopy

The discovery of Forster resonance energy transfer (FRET)1 has revolutionized our ability to measure inter- and intramolecular distances on the nanometre scale using fluorescence imaging. The phenomenon is based on electromagnetic-field-mediated energy transfer from an optically excited donor to an acceptor. We replace the acceptor molecule with a metallic film and use the measured energy transfer efficiency from donor molecules to metal surface plasmons(2) to accurately deduce the distance between the molecules and metal. Like FRET, this makes it possible to localize emitters with nanometre accuracy, but the distance range over which efficient energy transfer takes place is an order of magnitude larger than for conventional FRET. This creates a new way to localize fluorescent entities on a molecular scale, over a distance range of more than 100 nm. We demonstrate the power of this method by profiling the basal lipid membrane of living cells.