Hemoglobin Richmond, a Human Hemoglobin Which Forms Asymmetric Hybrids with Other Hemoglobins

The discovery of an abnormal hemoglobin variant (hemoglobin Richmond) in several members of a Negro family is reported. Structural analyses indicated a replacement of asparaginyl residue G4(102)β by a lysyl residue, while no other abnormality has been found. Carriers of this hemoglobin abnormality are clinically and hematologically normal; oxygen dissociation curves of total blood and of red cell hemolysates from carriers do not differ significantly from those observed for normal individuals. Hb Richmond is able to form asymmetric hybrid hemoglobins of the α a α x β r β x type with various human hemoglobin variants; these hybrids are readily detectable by electrophoresis at pH 9.0. Formation of these hybrids was most pronounced at low temperature. The tetrameric hemoglobin dissociates readily into dimeric subunits in NaCl solutions of moderate ionic strength, at which hemoglobin A does not dissociate significantly. A similar phenomenon was also observed in buffers of both low and high pH.