Ionic selectivity revisited: the role of kinetic and equilibrium processes in ion permeation through channels

The intent of this paper is to bring up to date an earlier theory of equilibrium selectivity, with emphasis on making it applicable to the permeation of membrane channels and carriers, which involve kinetic considerations. The authors will review critically and unify a number of conceptual advances that have occurred since 1961, particularly the recognition by Hille of how the same energetic principles that describe equilibrium selectivity of binding sites also apply to the peaks of the energy barriers (the so-called selectivity filters) involved in the kinetics of permeation.