Neurofilaments are protein polymers localized to the cytoskeleton of neuronal cells and have physical characteristics that differentiate them from other biopolymers. Neurofilaments are approximately 15 nm in diameter and many microns long, with persistence length less than 1 micron. Extending away from the core of the filament are large unstructured polypeptides that have hydrodynamic diameters ranging from 50 to 110 nm, depending on their extent of phosphorylation. These unstructured sidearms have net charges ranging from near neutrality to -110 per Mr = 50,000. Changes in electrostatic charge alter the effective volume of these brush-like polymers, and interactions of the anionic polymers with polyvalent cations lead to aggregation and re-solubilization that appears to coincide with charge reversal of the polyelectrolyte filaments.