Figure 3.

SAXS measurements of bilayer properties. (a) Intensity versus momentum transfer (q) plots of small-angle x-ray scattering (SAXS) data collected from 50 nm liposomes under the same experimental conditions used for single-channel and ⁸⁶Rb⁺ flux assays. (b) Electron density profiles calculated from SAXS data using a 3-Gaussian model. Specific parameters averaged from three experiments are characterized in Table 1. (c) The function of E71A KcsA channels measured by ⁸⁶Rb⁺ flux was re-plotted against estimates of hydrophobic thickness from SAXS experiments (●) (Table 2) or from the average of the MD simulations (○) (Table 3). These data indicate that channel activity is modulated drastically with sensitivities in a range as narrow as 0.5–3 Å.