Figure 3.

The KcsA K+ channel (helical ribbons) embedded in an explicit dipalmitoyl phosphatidylcholine (DPPC) phospholipid membrane (stick figures; fatty acids are white and head groups are red, green, and white) bathed by a 150 mM KCl aqueous salt solution (blue and green spheres represent potassium and chloride ions, respectively, and water molecules outside the membrane are shown in blue). The simulation system, consisting of 40,000 atoms, was used to compute a multi-ion PMF governing ion conduction³³ through the channel and to determine the sources of its ionic selectivity.⁷²³ (from Bernèche & Roux³³).