Charge Distributions That Cause Current to Enter a Pore in a Biological Membrane

Charge distributions within and surrounding a pore in a biological membrane are calculated using a Coulomb law based analysis. Prior to the formation of the pore, each side of the membrane has a uniform free charge distribution, with positive charges on the membrane\´s extracellular side and negative charges on its intracellular side. Upon formation of the pore, the charges in the immediate vicinity of the pore rapidly redistribute with time constants based on the relaxation time of the biological medium. Thereafter, the charge distributions on both sides of the membrane decay much more slowly, e.g., 100 or more times slower based on the resistance of the pore and system\´s overall capacitance. The initial rapid charge redistribution is needed so that current will turn into the pore on the extracellular side and turn outward from the pore on the intracellular side during the period of slower relaxation. The rapid redistribution includes the formation of charge regions ("turning charges") just inside the entrance and exit ends of the pore that have a sign opposite to that of the charges on the adjacent extracellular and intracellular surfaces. Interestingly, the charged amino acid residues believed to be located at the mouth of certain biological pores have distributions similar to these "turning charges".