New Manuscript: PNAS

October 17, 2017

Mechanically switching single-molecule fluorescence of GFP by unfolding and refolding. We use optical tweezers to force single molecules of GFP into folding and unfolding intermediate states and simultaneously probe single-molecule fluorescence from each state. Our results show that fluorescence is lost during the earliest events in unfolding, 3.5 ms before secondary structure is disrupted. No fluorescence is observed from the unfolding intermediates or the ensemble of compact and extended states populated during refolding. We further demonstrate that GFP can be mechanically switched between emissive and dark states. These data definitively establish that complete structural integrity is necessary to observe single-molecule fluorescence of GFP. Read more…