FIGURE 13.

The theoretical free energy difference compared to the experimental data of Perozo et al. (2002a) for different choices of the geometric parameters characterizing the open-state thickness. The thickness deformation energy is plotted for a closed-state thickness of W_C = 37.5 Å and several different open-state thicknesses. Each curve is shifted to pass through the data point at an acyl-chain length of 16. An open-state thickness of W_O ∼ 36 Å gave a reasonable fit to the experimental data. Perozo and co-workers also have electron paramagnetic resonance data for bilayers with acyl-chain lengths n ≥ 10, which suggest that the channel is closed (ΔG ≥ 0) in the absence of applied tension.