This Demonstration illustrates the fraction () of a two‐state protein (or other biomolecule) that has melted at temperature . The two states of the protein are denoted (native or folded) and (denatured or melted) and we consider the dynamic equilibrium . The ratio of the two states' equilibrium concentrations is , where ) is the standard state Gibbs free energy difference and is the universal gas constant (8.314 J/mol-K). Melting occurs when (i.e., ). . The parameter (standard state enthalpy difference) controls the steepness of the transition, but does not affect the location of the point where . The temperature () at which is and .