Circular dichroism and absorption spectra of haemoglobin Bart's

Circular dichroism spectra of haemoglobin Bart's (γ₄) in the region from 240 to 600 nm were different from those of human adult haemoglobin, but closely similar to those of the β-subunit of human adult haemoglobin. The amplitude of the positive circular dichroism maximum of deoxygenated haemoglobin Bart's in the Soret region was much less than that of human adult haemoglobin. The peak molar extinction coefficient of deoxygenated haemoglobin Bart's in the Soret region was found to be lower than that of deoxygenated human adult haemoglobin. These data indicate that haemoglobin Bart's, which is composed of four identical chains and lacks co-operativity, is structurally similar to haemoglobin H (β₄).