Complexation of a polyelectrolyte with oppositely charged spherical macroions: Giant inversion of charge

Complexation of a long flexible polyelectrolyte (PE) molecule with opposite ly charged spherical particles such as colloids, micelles, or globular prot eins in a salty water solution is studied. PE binds spheres winding around them, while spheres repel each other and form almost periodic necklace. If the total charge of PE in the solution is larger than total charge of spher es, repulsive correlations of PE turns on a sphere lead to inversion of the net charge of each sphere. In the opposite case when the total charge of s pheres is larger, we predict another correlation effect; spheres bind to th e PE in such a great number that they invert the charge of the PE. The inve rted charge by absolute value can be larger than the bare charge of PE even when screening by monovalent salt is weak. At larger concentrations of mon ovalent salt, the inverted charge can reach giant proportions. Near the iso electric point where total charges of spheres and PE are equal, necklaces c ondense into macroscopic bundles. Our theory is in qualitative agreement wi th recent experiments on micelles-PE systems. (C) 2001 American Institute o f Physics.