Dragavon, J., et al. Proc. Natl. Acad. Sci. USA 109, 8890–8895 (2012).

Under the right conditions, nonradiative energy transfer occurs between a bioluminescent donor and a fluorescent acceptor molecule. This phenomenon, termed bioluminescence resonant energy transfer (BRET), requires that the participating molecules have spectral overlap and that they are in close proximity (10 nanometers apart or less). Dragavon et al. show that bioluminescent light can also excite fluorescence in a radiative process in which the excitation light travels over distances too large to be compatible with BRET. They demonstrated this phenomenon in vitro and in vivo using bacteria expressing the lux operon from Photorhabdus luminescens (donor) and red-emitting quantum dots (receptor). Although the applications of this approach remain to be fully realized, the results suggest that additional controls may be needed to interpret BRET data.