Kinetics of HB S gelation. Effect of alkylureas, ionic strength and other hemoglobins

Using a light scattering (turbidity) method to estimate the delay time of gelation of deoxy hemoglobin S hemolysates, we have examined the effects of various alkylureas, variations in ionic strength by addition of NaCl, and admixture with other hemoglobins on gelation kinetics. Each of these factors substantially prolonged the delay times to different extents, but the dependence of the delay times on a high power of the hemoglobin concentration varied only slightly. These findings suggest that the events preceding gelation, most likely the formation of nuclei, are affected by these factors, but the critical nuclear size for gelling is fairly constant. Parallel changes indicated good qualitative correlation between gelation, delay times, minimum gelling concentrations of solutions of mixed hemoglobins and kinetics of sickling of red cells containing these mixtures, with the exception of hemoglobin Charlem trait cells the sickling kinetics of which were slower than predicted by the solution properties.