Dissociation of human haemoglobin at low pH

Abstract

Measurements were made of the sedimentation and diffusion of human carboxyhemoglobin, over ranges of pH, buffer composition, concentration and in the presence and absence of urea or Cu. Results show that these properties of the protein are independent of conditions between pH 6 and 11; between 3.5 and 6 a rapidly reversible dissociation occurs into particles of about half the particle weight and about the same frictional ratio as that of the undissociated material. Below pH 3.5, or on prolonged exposure to pH 5, an irreversible denaturation occurs. The dissociation is increased by dilution, by lowered pH and by the presence of urea and barbltone. Cu induces reassociation of partially denatured material but is without effect on native hemoglobin.