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. Author manuscript; available in PMC: 2021 Jun 20.
Published in final edited form as: Annu Rev Biochem. 2020 Jun 20;89:443–470. doi: 10.1146/annurev-biochem-013118-111442

Figure 3.

Figure 3

The free energy landscape changes in response to applied force. (a) As force is increased (red), the free energy landscape will tilt about the line −Fx. Note that force changes both the difference in free energy of the states 1 and 2, favoring state 2, and the height of the barrier, accelerating unfolding and resulting in a shift in equilibrium toward the unfolded state. Because the magnitude of the mechanical perturbation is proportional to the extension, longer states are affected more than shorter states. (b) Illustration of the origin of the stretching free energy that results from a shift in the state minimum; ΔGstretch is illustrated here for state 2. State 1 is similarly affected, but at a lesser magnitude.