The energy used or expended in an equilibrium binding reaction is described by the equation,

ΔG^o = ΔH^o –TΔS^o

where G^o is the Gibbs Free Energy, H^o is enthalpy, T is the absolute temperature (in ^oK), and S^o is entropy.

The change in Gibbs Free Energy, ΔG^o, is related to the dissociation constant for binding, K_D, by the equation,

ΔG^o = RT ln K_D,

where R is the gas constant [1.98722 cal/^oK•mol], and T is the absolute temperature.

Biacore^® instrument measurements of K_D as a function of temperature, T, can therefore reveal the enthalpy and entropy of any binding reaction, from the following relationship:

ln K_D = ΔH^o/RT – ΔS^o/R

Thus, measuring K_D as a function of T yields information about the thermodynamics of the binding reaction.