Proton-dependent dissociation equilibrium of hemoglobin. 2. Surface pressure measurements in monolayers of horse hemoglobin (III).

The molecular weight of hemoglobin (III) in monolayers on aqueous subsolutions has been determined by measuring the surface pressure as a function of the protein surface concentration. The dissociation equilibrium between tetrameric and dimeric hemoglobin (III) was determined for spread as well as adsorbed monolayers. The results were compared with analogous measurements in solution. It was found that the numerical value and the pH dependence of the dissociation constant were similar both in the bulk and in the surface phase of the solution. From these findings it was concluded that the native conformation of hemoglobin (III) is retained after adsorption at aqueous surface.