On the cooperativity of the thermal denaturation of mini-proteins

It is well established that the reversible thermal denaturation of small globular proteins is a cooperative two-state transition, analogous to a first-order phase transition in a finite-size system. Finite-size effects on the cooperativity of the reversible thermal denaturation become more important when the polypeptide chain is very small, as in the case of some synthesized mini-proteins. The analysis of two specific examples of mini-proteins, by means of a statistical mechanical approach, leads to the conclusion that their thermal denaturation, in view of its broadness and energetics, cannot be considered a cooperative first-order phase transition.