DNA condensation, redissolution and mesocrystals induced by tetravalent counterions

Abstract

The distance-resolved effective interaction potential between twoparallel DNA molecules is calculated by computer simulations withexplicit tetravalent counterions and monovalent salt. Addingcounterions first yields an attractive minimum in the potentialat short distances which then disappears in favor of a shallowerminimum at larger separations. The resulting phase diagramincludes a DNA condensation and redissolution transition and astable mesocrystal with an intermediate lattice constant for highcounterion concentration.