Fig. 4.

Activation energy for water flux across KcsA channels. Osmotic volume flux-induced Mg²⁺ dilution was measured as a function of temperature. Reconstitution of KcsA channels increased G from 3 nS·cm^–2 (bare bilayer) to 20 mS·cm^–2. (Inset) Arrhenius plot for water flow across protein-free lipid bilayers and KcsA containing bilayers. From the slope, an activation energy of ≈14 kcal/mol was obtained for protein-free lipid bilayers (filled circles). Protein reconstitution decreased the activation energy (open squares). The incremental water permeability caused by KcsA corresponds to an activation energy of 5.1 kcal/mol (solid line).