AN α-THALASSEMIA FAMILY PRODUCING HEMOGLOBIN H AND ITS MODIFIED PIGMENT ELECTROPHORETICALLY INDISTINGUISHABLE FROM Hb BART’S
An α-Thalassemia family producing two electrophoretically fast-moving components of hemoglobins in addition to normal hemoglobins was encountered in our laboratories. The proband was a 23- year-old Thai female with microcytic hypochromic hemolytic anemia. The same abnormalities were seen also in her two sisters and in her father. Of the two abnormal hemoglobins, the faster component (F-l) migrated to the position of ordinary Hb H, while another to that of Hb Bart's. However, the identity of both of these pigments with Hb H was established by globin dissociation (into α and β chain) starch gel electrophoresis, fingeprinting and amino acid analyses. The differences in characters between the two pigments were as follows : 1) there was heme depletion, and the heme contents of F-l and F-2 were 85 and 77% of the theoretically expected, respectively. 2) titrative PCMB consumption was not equal (F-l = 8.0, F-2 = 7.2, Hb A = 2.0 mol PCMB/ mol-Hb). Tryptophan notch (289 nm) was not seen in both F-l and F-2 just like in Hb A. Hemichrome absorption spectra instead of those of met Hb were seen in F-l and F-2 in the process of oxidation. Oxygen affinity of these two pigments was increased over that of Hb A (F-l and F-2, P50≒0.3; Hb A, 5.2-12.5 mmHg) with neither significant heme-heme interaction (Hill's n = 1.0 in F-l and F-2; n=2.6 in Hb A) nor the Bohr effect. From these findings it was presumed that F-l was Hb H, and F-2 would be its modification generated by more marked heme depletion (23 %). The component F-2 should not be confused with Hb Bart's because they will behave electrophoretically in the same way.
