Solubilities of naturally occurring mixtures of human hemoglobin

Abstract

The phase-rule behavior of amorphous human ferrohemoglobin has been studied. The salting-out of hemoglobin in this form apparently resulted in the rapid attainment of a true, metastable solubility equilibrium. The solubility behavior of normal adult ferrohemoglobin in the amorphous state was that of homogeneous protein in a single solid phase. The solubility behavior of the amorphous solid formed by the salting-out of mixtures of ferrohemoglobins was that of a solid solution. A standard solubility test for examining naturally occurring mixtures of human hemoglobin has been described. Under the conditions of this test, specimens that contained sickle-cell hemoglobin formed amorphous precipitates at a phosphate concentration of 2.24 M, while all other specimens dissolved completely. Within the former group, sickle-cell trait specimens had the highest solubilities and sickle-cell anemia specimens the lowest. The less common modifications of sickle-cell disease were associated with intermediate solubilities. Specimens that failed to precipitate in 2.24 M phosphate were compared in 2.58 M phosphate. The solubility of one specimen of hemoglobin C was more than twice that of normal adult hemoglobin. The hemoglobin mixture in hemoglobin C trait was found to have a significantly higher total solubility than normal adult hemoglobin. Mixtures of normal adult and fetal hemoglobin also had higher solubilities than normal adult hemoglobin. The solubility method is suitable for the determination of the approximate hemoglobin S content of a mixture.