Molecular structure study on the polyelectrolyte properties of actin filaments

An accurate characterization of the polyelectrolyte properties of actin filaments might provide a deeper understanding of the fundamental mechanisms governing the intracellular ionic wave packet propagation in neurons. Infinitely long cylindrical models for actin filaments and approximate electrochemical theories for the electrolyte solutions were recently used to characterize these properties in in vitro and intracellular conditions. This article uses a molecular structure model for actin filaments to investigate the impact of roughness and finite size on the mean electrical potential, ionic density distributions, currents, and conductivities. We solved the electrochemical theories numerically without further approximations. Our findings bring new insights into the electrochemical interactions between a filament's irregular surface charge density and the surrounding medium. The irregular shape of the filament structure model generated pockets, or hot spots, where the current density reached higher or lower magnitudes than those in neighboring areas throughout the filament surface. It also revealed the formation of a well-defined asymmetric electrical double layer with a thickness larger than that commonly used for symmetric models.