Measurements of the hysteresis in unzipping and rezipping double-stranded DNA

Complete unzipping and rezipping of lambda-phage double-stranded DNA is achieved by applying a constant force. A strong hysteresis is observed at all tested time scales and temperatures. Hysteresis also occurs for partial unzipping, indicating stability for the partially open state over a force range of 2-5 pN. Results are compared to nearest-neighbor model simulations, and reasonable agreement is found.