  Monte Carlo simulations were employed to study two charged rods confined
between two unlike charged plates, all immersed in a model electrolyte.
Recently, it was shown that two rods immersed in a multivalent counterion
solution may show attraction (PRL 78, 2477 (1997)). Here we show for a
monovalent electrolyte that rod-rod attraction and repulsion can switch sign
depending on confinement and ionic size. We also propose a simple
self-assembling mechanism which may be helpful to understand the DNA-lipid
bilayers complexation.
