Extreme Dependence of Dynamics on Concentration in Highly Crowded Polyelectrolyte Solutions

Charge carrying species, such as polyelectrolytes, are vital to natural and synthetic processes that rely on their dynamic behavior. Using single-particle tracking techniques, the diffusivity of individual polyelectrolyte chains and overall system viscosity are determined for concentrated polylysine solutions. These studies show experimental scaling dependences much stronger than theoretical predictions for both neutral polymers and polyelectrolytes. Similar dependences are observed in concentrated solutions prepared at a variety of pH and counterion conditions. Hindered system dynamics are attributed to contributions from monomeric friction and the large effective excluded volume of polyelectrolyte chains. These forces restrict the movement of polymers through the sample and their effects are seen over a wide range of concentrations. The framework of the Ventras Duda free volume theory is used to compare polyelectrolyte and neutral systems. Overall, these results are applicable to behavior in crowded biological systems, such as intracellular environments where the mobility of proteins is strongly inhibited.