Figure 2.

Divalent cation translocation mechanism. (A) Translocation rate of divalent cations through the 1:1 DOPC:DOPA membrane extracted from intensity decay in SH images. (B) Transmembrane potential values induced by a 5 mM divalent cation solution on one side of 1:1 symmetric DPhPC:DPhPA GUVs. Each dot represents the average potential value of a single GUV and the colored lines represent the domain-wise spread in membrane potential. (C) Computed free energy of pore formation in the POPC lipid membrane (black curve - simulation) together with experimental values for Ba²⁺, Ca²⁺, and Cu²⁺ ions (colored squares - experiment) extracted from measured translocation rates. (D) MD snapshot of an open pore at a transmembrane potential magnitude of 600 mV in a POPC:POPS membrane. Lipid phosphorus atoms are rendered as brown spheres, lipid tails as gray lines, and Ca²⁺ ions as yellow spheres. Water molecules inside the membrane are represented as sticks and bulk water as a transparent surface. (E) Schematic of the voltage-induced ion transport mechanism. Transmembrane potential induced by divalent cation binding opens a transient pore through which divalent cations can translocate from one side of the membrane to the other.