Materials for Fluorescence Resonance Energy Transfer Analysis: Beyond Traditional Donor-Acceptor Combinations

The use of Förster or fluorescence resonance energy transfer (FRET) as a spectroscopic technique has been in practice for over 50 years. A search of ISI Web of Science with just the acronym “FRET” returns more than 2300 citations from various areas such as structural elucidation of biological molecules and their interactions, in vitro assays, in vivo monitoring in cellular research, nucleic acid analysis, signal transduction, light harvesting and metallic nanomaterials. The advent of new classes of fluorophores including nanocrystals, nanoparticles, polymers, and genetically encoded proteins, in conjunction with ever more sophisticated equipment, has been vital in this development. This review gives a critical overview of the major classes of fluorophore materials that may act as donor, acceptor, or both in a FRET configuration. We focus in particular on the benefits and limitations of these materials and their combinations, as well as the available methods of bioconjugation. Dye another day: Modern donor and acceptor materials for fluorescence resonance energy transfer (FRET) analyses (see picture) comprise photochromic dyes, semiconductor nanocrystals, nanoparticles, fluorescent amino acids, polymers, and genetically encoded protein, in additional to “traditional” organic dyes. The scope and boundaries of such systems, as well as avaible methods for bioconjugation are discussed, with an emphasis on the combination of different materials.