Zeta potential depiction of PF4 and heparin colloidal interactions. Y-axis represents positive or negative electrostatic potential as a function of increasing concentrations of UFH (on x-axis). (A) Positively charged PF4 molecules remain stably dispersed in the absence of heparin due to repulsive interactions. (B) With increasing amounts of heparin, PF4 charges are neutralized promoting floc or macromolecular assembly. (C) With heparin in molar excess, repulsive interactions once again predominate, leading to stable dispersion of smaller particles.