Letter: Analysis of hemoglobin aggregation from Gibbs-Donnan equilibrium experiments

Dear Sir: Gary-Bobo and Solomon (1968, 1971) have employed Gibbs-Donnan equilibrium studies in the assessment o f the anomalous osmotic behavior o f the red cell. In these studies, the interpretation was based on thermodynamic equations for ideal solutions. During the course of recent investigations, we have found that it is necessary to consider the nonideal aspects o f concentrated hemoglobin solutions. In this letter, we have transformed the ideal equations o f Gary-Bobo and Solomon to include nonideal contributions for the interpretation o f hemoglobin-hemoglobin and hemogiobin-solution interactions. Experimentally, Gary-Bobo and Solomon (1968, 1971) measured the Donnan equilibr ium of hemoglobin-potassium chloride solutions. The Donnan ratio, r, is defined in Eq. 1, where [K+]ln is the molal potassium