Figure 6.

Combination of optical trapping and Förster resonance energy transfer (FRET) in the experimental setup devised by Brenner et al. [95]. The end-to-end extension of the repeat protein made of spider silk peptides is measured by FRET, while optical tweezers are used to apply forces. Trapping laser and fluorescence excitation are kept well apart by long double-stranded DNA (dsDNA) handles. Reprinted with permission from [95]. Copyright 2016 American Chemical Society.