Phase diagram of the Wako-Saito-Munoz-Eaton β hairpin model obtained from the partition-function zeros

I study the partition-function zeros of the Wako-Sait-Muoz-Eaton (WSME) beta hairpin model in the complex temperature plane when the number of native contacts is 10. For various values of the entropy cost of disordering a bond, the zeros show a clear locus corresponding to the folding transition. The result suggests a new definition of the transition temperature, the temperature obtained by extrapolating the locus to the positive real axis. By computing the transition temperature for various values of the entropy cost, we obtain the phase diagram of the WSME beta hairpin model. I compare the present definition of the transition temperature with the transition midpoint temperature for several values of the entropy parameter and show that they are in a reasonably good agreement.