A Structural Interpretation of the Acidity of Groups Associated With the Hemes of Hemoglobin and Hemoglobin Derivatives

Since the discovery by Bohr and coworkers in 1904 of the effect of acidity on the oxygen equilibrium of hemoglobin, there have been a large number of investigations directed towards clarification of the physicochemical relationships of acid groups with the hemes in hemoglobin and its derivatives. It is the purpose of this paper to analyze modern quantitative data, including those for ferrihemoglobin (methemoglobin), in order to throw new light on the general problem, to establish the ionization constant of an acid group in ferrihemoglobin previously unrecognized, and to give a structural interpretation of shifts in the pK of groups caused by changing chemical environment.