An integral equation study of reentrant behavior in attractive interactions between like-charged macroions immersed in an electrolyte solution

The effective interaction between two like-charged macroions immersed in an electrolyte solution was studied using a Ornstein-Zernike equation with hypernetted-chain closure (HNC-OZ theory) with a particle model for the ions and solvent molecules to discuss some biological phenomena. We examined conditions under which the Coulomb interaction was greater than the thermal energy. Although the macroions repelled each other in a dilute electrolyte solution, a strong effective attraction between macroions occurred only in a medium concentration electrolyte. The effective interaction is analyzed using the superposition approximation to discuss the bond formation. When the effective attraction appears, the dense cloud of countercharged ion exists between the macroions and the cloud mediates the attraction like a covalent bond.