Melting mechanisms of DNA-linked nanocomposite systems

The origins of sharp melting transitions in DNA-linked nanocomposite systems are discussed. Under typical experimental conditions, the local salt concentration in DNA-linked nanocomposite systems is important, leading to salt-induced condensation both in DNA-linked gold nanoparticle systems and polymer-DNA hybrid systems that leads to cooperative melting. Although this coop-erativity is supported by the experimental results, which have measured the number of cooperative DNA sequences, and molecular dynamics simulations, some recent experiments suggest that the sharp melting does not arise entirely from salt condensation. We point out that this discrepancy can be resolved by considering the contribution of large clusters, which only exist below the melting transition.