Dissociation of DNA–polycation complexes by polyanions and polyampholytes

Both polyanions and polyampholytes cause the dissociation of DNA–polycation complexes in experiments. To elucidate their mechanisms, Monte Carlo simulations have been conducted on a simple model, with DNA modeled as an infinite charged cylinder and other polyions treated as charged Shish–Kebab rods. Our results show that a highly charged polyanion is required to separate a polycation from a DNA. However, for a diblocked polyampholyte, its net dipole induces a higher probability to bridge a DNA and a polycation. Thus, the loosening mechanisms are found to be markedly different between polyanions and polyampholytes.