DONNAN POTENTIALS GENERATED BY THE SURFACE CHARGE ON STRIATED MUSCLE FILAMENTS.

The crystalline characteristics and the deformability of the array of myosin rods, which comprises the A-band of striated muscle, has led to the conceptualization of this structure as a smectic B//1 liquid crystal. It is plausible that intermolecular forces stabilize the A-bands and that the repulsive component of the necessary force-balance results from the electrostatic surface charge on the myosin rods and the interdigitating actin filaments. Before this theory may be resolved, one needs to determine the surface charge along the myosin rods and actin filaments. These surface charges may be obtained by measuring electrochemical potentials. Such potentials are Donnan in origin, arising from an equilibrium condition in which charged structural components in one phase of a two-phase ionic system cause an unequal distribution of diffusible ions. The lattice of charged myofilaments in an ionic solution satisfies these criteria.