AMaSiS 2018 Workshop: Abstracts

Ions in solutions and channels: Physical and biological plasmas

Robert Eisenberg${}^{\mathbf{\text{(1,2)}}}$

(1) Rush University Medical Center, Dept. of Physiology and Biophysics, Chicago

(2) Illinois Institute of Technology, Dept. of Applied Mathematics, Chicago

Ion channels are proteins with a hole down their middle that conduct ions (spherical charges like Na${}^{+}$, K${}^{+}$ , Ca${}^{2+}$, and Cl${}^{-}$ with diameter $\sim$ 0.2 nm) through a narrow tunnel of fixed charge (‘doping’) with diameter $\sim$ 0.6 nm. Ionic channels control the movement of electric charge and current across biological membranes and so play a role in biology as significant as the role of transistors in computers: a substantial fraction of all drugs used by physicians act on channels.

Channels can be studied in the tradition of physical science. Poisson-Drift diffusion equations familiar in plasma and semiconductor physics — called Poisson Nernst Planck or PNP in biology — form an adequate model of current voltage relations in many types of channels under many conditions if extended to include correlations. They can be further extended to describe ‘chemical’ phenomena like selectivity with some success.

Ionic channels are manipulated with the powerful techniques of molecular biology in hundreds of laboratories. Atoms (and thus charges) can be substituted a few at a time and the location of every atom can be determined in favorable cases. Ionic channels are one of the few living systems of great importance whose natural biological function can be well described by a tractable set of equations. The plasmas of biology can be analyzed like the plasmas of physics.