Two abnormal hemoglobin components have been detected in association with thalassemiahemoglobin H disease. These components, as well as the major hemoglobin component, have been chemically characterized by determination of the amino acid composition, N-terminal amino acid sequence, tryptic peptide patterns, sedimentation coefficients, and subunit hybridization. The abnormal component in larger amount has a subunit formula of β_4; the abnormal component in smaller amount has a subunit formula of γ_4. The major hemoglobin component could not be distinguished chemically from normal hemoglobin A. Subunit hybridization studies of hemoglobins indicate that the affinities of the various subunits for one another are not equal
