Circular Dichroism of Hemoglobin and Its Subunits in the Soret Region

The circular dichroism of human hemoglobin and its isolated chains has been measured in the 210 to 460 mµ region. In the Soret region, human hemoglobin exhibits a complex circular dichroism with a large positive extremum and a small negative trough. Although α and β chains are much alike in tertiary structure, α chains exhibit a single positive band and β chains give a complex circular dichroism with a positive and a negative band in the Soret region. The circular dichroism spectra of reconstituted hemoglobin, which are essentially identical with those of native hemoglobin, are not simply the sum of the circular dichroism spectra of the isolated subunits. The positive ellipticity of deoxygenated hemoglobin is about twice as great as the value calculated from those of the isolated chains. Horse heart myoglobin exhibits a single positive band similar to that of α chains.