Diffusion and reaction rate theories provide convenient approaches for describing permeation in ionic channels. Both approaches have strengths and weaknesses. Diffusion theories realistically approximate the physical process of ion movement within an aqueous pore, but those theories do not handle ionic interactions easily. Reaction rate theories are easy to use, and they provide a mathematical summarization of the data that is valuable for communicating experimental results. During ion permeation, however, the basic assumptions of reaction rate theory are not met. Therefore, rate theories do not provide true physical descriptions of ion permeation.
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This work was supported by grants to J.A.D. from NIH (NS21229) and from the Muscular Dystrophy Association.