Fig. 6.
Hb composition of three fractions of erythrocytes separated by density gradient centrifugation of blood from an untransfused HbE/β+ thalassemic [IVS 1-5(G-C)], separating red blood cells into top (least dense, youngest cells), middle, and bottom (densest, oldest cells). Each point is the average of two centrifugations from the same patient. The ratio of HbE/HbA increases slightly as the red blood cells age, suggesting that HbE is at least as stable as HbA; the ratio of HbF/HbA increases with cell age as expected. The decrease in pyruvate kinase activity with increasing cell density confirms that the denser fractions contain predominantly older red blood cells. (○) %E/%A; (•) %F/%A; (×) PK.