Opening rates of DNA hairpins: experiment and model.

We present single-molecule measurements of the opening rate of DNA hairpins under mechanical tension and compare with the results obtained from a reduced-degrees-of-freedom statistical mechanics model. We extract the apparent position of the transition state s and find that the model, with no fitting parameters, reproduces the experimental measurements surprisingly well. Our values for s are different from the ones obtained in previous experiments, where, however, the experimental conditions were different (different force fields, different salt concentrations). Thus it appears that the values of s measured for relatively short hairpins are strongly affected by these experimental conditions.