A simple model of protein cold denaturation

Cold denaturation is a general feature of the conformational stability of globular proteins. Its modelization is still an important goal of biophysics. We present a modified version of the Schellman-Brandts model that is able to reproduce the occurrence of two conformational transitions, cold and hot denaturations. The model suggests that: (a) globular protein cooperativity can be obtained by distinguishing an inner core, buried from water contact, in a spherical globule; (b) the latter is stabilized by the hydrophobic effect that can be modelled by the Gibbs free energy gain associated with the burial of nonpolar side chains in the inner core; (c) cold denaturation comes from the decrease in the stabilization provided by the hydrophobic effect at low temperature.