Modified Poisson-Boltzmann theory for solution of divalent rod-like ions

A. Razinger (1), K. Bohinc (1,2), A. Iglic (1), S. May (3), V. Kralj-Iglic (1,4)

(1) Faculty of Electrical Engineering, Ljubljana, Slovenia; (2) University College of Health Care, Ljubljana, Slovenia; (3) Department of Physics, North Dakota State University, Fargo, U.S.A.; (4) Faculty of Medicine, Ljubljana, Slovenia

Attractive interactions between identical like-charged macroions in aqueous multivalent salt solution arise due to ion-ion correlations. The mean-field level Poisson-Boltzmann (PB) theory does not predict such behavior for point-like structureless ions. Various multivalent ions, such as certain DNA condensing agents or short stiff polyelectrolytes, do have an internal, often rod-like, structure. Applying modified PB theory to the generic case of divalent rod-like salt ions, we found attraction between like-charged macroions above a critical distance between the two individual charges of the rod-like ions. We calculated this distance analytically within linearized PB theory. The average orientation of divalent rod-like ions was calculated as a function of the distance from the charged surface of the macroions. References: K.Bohinc, A. Iglic, S. May: Interaction between macroions mediated by divalent rod-like ions, Europhys. Lett., 68:494-500 (2004).

Email: ales.iglic@fe.uni-lj.si

Address: prof. dr. Ales Iglic, Group of Applied Physics, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana, Slovenia