Counterion correlations and attraction between like-charged macromolecules- art. no. 011804

A simple model is presented for the appearance of attraction between two li ke-charged polyions inside a polyelectrolyte solution. The polyions are mod eled as rigid cylinders in a continuum dielectric solvent. The strong elect rostatic interaction between the polyions and the counterions results in co unterion condensation. If the two polyions are sufficiently close to each o ther their layers of condensed counterions can become correlated resulting in attraction between the macromolecules. To explore the counterion induced attraction we calculate the correlation functions for the condensed counte rions. It is found that the correlations are of very short range. For the p arameters specific to the double stranded DNA, the correlations and the att raction appear only when the surface-to-surface separation is less than 7 A ngstrom.