title: Effect of protein-protein interactions on binding of ligands by proteins.
abstract: In general, saturation curves for ligand binding by proteins are described by the Adair-equation. The approach to ligand binding with methods of statistical mechanics leads not only to expressions for the Adair-constants, but gives also the possibility of describing the effect of protein-protein interactions on the binding of ligands by proteins. Under the assumption of the superposition-approximation for the potential of mean force between proteins in a solution, which contains also ligand molecules, the variations of the second and third virial coefficient with ligand activity are calculated for several simple model-pontentials. Finally the pair potential of hemoglobin molecules known from X-ray measurements will be approximated by such a simple square-well potential. With that the effect of hemoglobin density on oxygenation will be estimated. One finds for our model system that at relatively high protein density a further increase in density should be accompanied by a decrease in affinity (hindrance of saturation) and an increasing steepness of the slope of the saturation curve.
mesh_terms: D002151:Calorimetry; D006454:Hemoglobins; D007700:Kinetics; D008024:Ligands; D008433:Mathematics; D010108:Oxyhemoglobins; D011485:Protein Binding; D011506:Proteins; D014961:X-Ray Diffraction
chemical_list: D006454:Hemoglobins; D008024:Ligands; D010108:Oxyhemoglobins; D011506:Proteins