Evolution of the Ca²⁺ conduction mechanism with increasing absolute value of effective fixed charge |Q_f|, showing the Coulomb blockade oscillations of multi-ion conduction/blockade states. The neutralized states Z_n providing blockade are interleaved with resonant conduction states M_n. The |Q_f| value increases from top to bottom, as shown. Green circles indicate Ca²⁺ ions, unfilled circles show vacancies (virtual empty states during the knock-on process). The right-hand column indicates the preliminary identifications of particular channels/mutants corresponding to particular mechanisms. Mutants studied here are shown in red.