The ability of actins and tubulins to change dynamically from alterations in the number density of actins/tubulin, number density and type of binding agents, and electrolyte concentration is crucial for eukaryotic cells to regulate their cytoskeleton conformations in different cellular compartments. Conventional approaches on biopolymers solution break down for cytoskeleton filaments because they entail several approximations to treat their polyelectrolyte and mechanical properties. In this article, we introduce a novel density functional theory for polydisperse, semiflexible cytoskeleton filaments. The approach accounts for the equilibrium polymerization kinetics, length, and orientation filament distributions, as well as the electrostatic interaction between filaments and the electrolyte. This is essential for cytoskeleton polymerization in different cell compartments generating filaments of different lengths, sometimes long enough to become semiflexible. We characterized the thermodynamics properties of actin filaments in electrolyte aqueous solutions. We calculated the free energy, pressure, chemical potential, and second virial coefficient for each filament conformation. We also calculated the phase diagram of actin filaments solution and compared it with available experimental data.
Theory for weakly polydisperse cytoskeleton filaments
