USE OF THE POISSON-BOLTZMANN EQUATION TO ESTIMATE THE ELECTROSTATIC FREE-ENERGY BARRIER FOR DIELECTRIC MODELS OF BIOLOGICAL ION CHANNELS

We have obtained the electrostatic free energy profile of a univalent positive ion as it is moved from a bulk electrolyte solution into a bi ological ion channel of various model forms. The form of the results w as unaffected by the method of calculation. We used a fully consistent nonlinearized Poisson-Boltzmann scheme, a fully consistent linearized Poisson-Boltzmann scheme, and hybrid scheme. The channel models we us ed were designed to (crudely) mimic the shape and imbedded charge and dipolar distributions for biological ion-selective channels (such as t he voltage-gated K+ ''shaker'' channel). The results obtained were acc ounted for on simple physical grounds.