A Presidential Patent [Patents].

There is only one U.S. president who is also a patentee. One might guess that the president is Thomas Jefferson, who invented many things and considered himself to be an inventor. Or, we might guess George Washington whose work as a surveyor and planter, not to mention commander-in-chief of the army, brought him into contact with the latest technology of the 18th century.

Charge distributions of active biological pores.

Charge distributions associated with active biological pores are calculated. The charge distributions include rings of reverse-sign, current-turning charges which surround the entrance and exit ends of the pore and cause current to turn into the pore at its entrance end (e.g., the intracellular side of a potassium pore) and to turn outward from the pore at its exit end (e.g., the extracellular side of a potassium pore). The magnitude and spatial extent of the rings depend directly on the magnitude of the current passing through the pore. In the absence of current, the rings disappear and when, for example, the pore's resistance becomes the dominant resistance in the system, the magnitude and spatial extent of the rings saturate. The reverse-sign, current-turning charges affect the local environment of proteins, such as ligand-binding proteins, known to reside adjacent to biological pores. The charges are thus expected to play a role in pore function such as by modulating the binding of charged species to the binding proteins.

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."