Principles and application of intrinsic Förster resonance energy transfer (iFRET) for label-free detection of native proteins

Abstract

Tryptophan residues in proteins of interest were evaluated as FRET donors to facilitate the development of a label-free protein detection system, coined intrinsic Forster (or fluorescence) resonance energy transfer (iFRET). iFRET fluorescence probes, composed of an efficient and tryptophan-specific FRET acceptor in addition to a target protein-specific ligand, selectively bind to the target proteins thereby enabling Forster resonance energy transfer between the protein tryptophan residues and the iFRET probe. We have developed efficient iFRET acceptor fluorophores and a deep UV microscope, which were successfully applied to detect native target proteins in live cells.