Figure 3.

Free energy G₀(z) (solid line, right-hand scale) and mean restoring force F(z) = dG₀(z)/dz (dashed line, left-hand scale) of extracting and unfolding the D and E helix of the G241C mutant of bacteriorhodopsin. Eq. 12 was used to estimate G₀(z) from linear approximations (Inset) to the second peak of eight force-versus-distance curves reported in figure 5, Oesterhelt et al. (8).