DNA melting in poor solvent

Abstract

The melting phase diagram of a double-stranded DNA in poor solvent, which promotes condensation, is studied using the pruned and enriched Rosenbluth method in a simple cubic lattice. For slightly poor solvent, melting temperature decreases linearly with the solvent quality, which later changes slope and starts increasing, as the melting line approaches the tri-critical collapse curve. First-order melting transition, as in good solvent, gives way to continuous transition, and then to further broadened transitions where the order parameter smoothly becomes zero as the temperature is increased. This is accompanied by a continuously varying crossover exponent along the secondorder transition line, hinting at a non-universal nature of the melting transition. Importantly, our results conform to the experimental findings qualitatively.