Effect of liganded hemoglobin S and hemoglobin A on the aggregation of deoxy-hemoglobin S.

The effect of the carbonmonoxy forms of Hb S and Hb A on the solubility and kinetics of the aggregation of deoxy-Hb S in concentrated phosphate buffer was studied. The delay time was prolonged exponentially when the ratios of CO-Hb S and CO-Hb A to deoxy-Hb S were increased. This increase in the delay time prior to aggregation can be explained by the decrease in the concentration of deoxy-Hb S. As with deoxy-Hb A, the n value for the delay time prior to the aggregation of deoxy Hb S was unaffected by CO-Hb S and CO-Hb A. Electrophoretic and spectrophotometric analyses of the composition of CO- and deoxy-Hbs A and S in the solution before and after aggregation showed that CO-Hb S co-polymerized with deoxy-Hb S but that CO-Hb A did not. The amount of CO-Hb S in the polymer phase depended on the initial fraction of the CO form of Hb S. The participation of CO-Hb S in the polymer phase was further confirmed by direct measurement of the absorption spectra of the polymer phase after it was dissolved in deoxygenated phosphate buffer. From these results, we concluded that nuclei are formed only from deoxy-Hb S, but that once nuclei are formed, CO-Hb S and deoxy-Hb A co-polymerize with deoxy-Hb S.