Figure 4.

Comparison of bilayer structural changes as revealed by solid-state ²H NMR for three different methods of applying external pressure (see Fig. 1, a−c). Solid-state ²H NMR spectra (left) and corresponding C−²H bond segmental order profiles (right) are shown as a function of segment index (i) for DMPC-d₅₄ bilayers in the liquid-crystalline (L_α) state at T = 45°C. (a) ²H NMR spectra and $\left|S_{\text{CD}}^{\left(i\right)}\right|$ order profiles showing bilayer deformation induced by increased dehydration pressure (gravimetric dehydration). (b) ²H NMR spectra and $\left|S_{\text{CD}}^{\left(i\right)}\right|$ order profiles as a function of osmotic pressure due to the presence of PEG 1500. (c) ²H NMR spectra and $\left|S_{\text{CD}}^{\left(i\right)}\right|$ order profiles obtained at different bulk hydrostatic pressures (data from Brown et al. (47) with permission of the American Physical Society). Note that a larger change in segmental order profiles is seen with application of dehydration or osmotic pressure than for hydrostatic pressure.