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濾器主要處于三個態(tài),一個三離子態(tài)和兩個兩離子態(tài),轉(zhuǎn)導過程用這三個態(tài)之間的相互躍遷來描述。