Figure 5. A Schematic Representation of GFP Unfolding via a Short-Lived Intermediate.

(F), (I), and (U) denote the folded, intermediate, and unfolded conformations of GFP. ΔX quantities correspond to experimentally observed extension changes (obs). X^F and X^I are the dimensions of the folded and intermediate states of GFP, estimated from structural data (struct). X^U1 and X^U2 are the true extensions (true) corresponding to the unfolding of the first and second portions of GFP (shown as flexible chains in green and purple, respectively). The true extension of the entire unfolded GFP molecule is X^U1 + X^U2. The table provides reference values estimated for 6–10 pN. Bottom right panel displays a characteristic “rip-transition-rip” during GFP unfolding.