A convenient method for the determination of the solubility of hemoglobin and modified hemoglobins

The removal of a single charged group can drastically alter the solubility of hemoglobin. Alterations in hemoglobin structure to make it of potential use as a blood substitute must produce derivatives which are sufficiently soluble to allow adequate oxygen delivery. We have developed a convenient method for examining modified hemoglobins. How the polymerization of Hemoglobin S is perturbed in the presence of modified hemoglobins is determined. To measure Hemoglobin S polymerization, a rapid temperature jump from 0 degree and a nitrogen atmosphere [1] are not required. In pH 7.4 phosphate buffers at concentrations greater than 2M containing sodium dithionite, dilute solutions (less than 1 mg/ml) of hemoglobin S aggregate at 30 degrees, or higher, after a delay time (minutes) which depends on the hemoglobin concentration. Light scattering can be used to quantify the extent of polymerization. Chemical modifications of Hemoglobin A can result in altered perturbation of Hemoglobin S polymerization as determined by this method. Modification of hemoglobin to provide suitable oxygen binding characteristics and crosslinking of subunits is a required preliminary to use of hemoglobin as an acellular blood substitute. These modifications often involve the elimination of charged groups from hemoglobin. Information on whether such modifications may have undesirable consequences with respect to solubility properties can be examined using the method described.