In this model , ion conduction involves transitions of three states , with one three - ion state and two two - ion states in the selectivity filter respectively . in equilibrium , the well - known nernst equation is deduced 在這一模型中,離子通道的選擇性過(guò)濾器主要處于三個(gè)態(tài),一個(gè)三離子態(tài)和兩個(gè)兩離子態(tài),轉(zhuǎn)導(dǎo)過(guò)程用這三個(gè)態(tài)之間的相互躍遷來(lái)描述。