Determination of whether a specific ligand-receptor interaction at equilibrium is enthalpy- and/or entropy-stabilized can be achieved by thermodynamic analysis, writes Robert Hitzemann. Enthalpy stabilization is usually associated with the formation of new bonds (e.g. hydrogen bonds and van der Waal's interactions) in the ligand-receptor-membrane array, whereas entropy stabilization is usually characterized by the displacement of ordered water molecules coupled to the formation of new hydrophobic interactions. The initial step in the receptor association is generally entropy stabilized. For some agonists and antagonists, this initial step is followed by one or more steps that are enthalpy stabilized. Interestingly, there is a wide diversity in the thermodynamics of agonist/ antagonist receptor binding, suggesting several different mechanisms of information transfer.
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