Figure 4.

The relationship between the equilibrium radius of the pore (R _eq) and the relative cation concentration in the vesicle (n ⁺/n _max⁡ ⁺). The relationship between n ⁺/n _max⁡ ⁺ and R _eq is derived from the minimization of the membrane bending energy. Note that an increase in the cation concentration (bold line) leads to an abrupt increase in the fusion pore radius, R _eq (i.e., the opening of the fusion pore), while, in the opposite direction (dotted line), a reduction in the cation concentration leads to an abrupt closure of the fusion pore.