Ion Permeation and Chemical Kinetics

The difficulties with and controversies surrounding the interpretation of electrophysiological data were highlighted in the recent Perspectives on Ion Permeation through membrane-spanning channels. The main issue was whether such data are more appropriately analyzed within the framework of chemical kinetics (Eyring’s Transition State Theory; Eyring, 1935) or the continuum electrodiffusional approach (Nernst-Planck Theory and its more modern extensions; see, e.g., Nonner et al., 1998). Cogent arguments were presented for both viewpoints. Their importance is in the physical insights each can generate. In the most commonly used treatments of kinetic modeling found in the physiological literature, the Eyring expression for the rate constant is presented as: