Structure dynamics of the hemoglobin mutants Hb Hôtel Dieu, HbG Philadelphia, HbJ Mexico, Hb St. Mandé and Hb San Diego, studied by nanosecond‐laser‐flash photolysis

Abstract

The kinetics of the change from the carboxy to the deoxy conformation of the mutated hemoglobins mentioned in the title and of normal human adult hemoglobin were determined from measurements of light absorption changes occurring up to 50 μs after nanosecond-laser photodissociation of the corresponding CO complexes. The spectral evolution of the mutated hemoglobins was found to be similar in its main features to that of normal hemoglobin. The kinetics could be decomposed into two phases with rates 1.1–1.8 × 10⁶s⁻¹ and 0.17–0.34 × 10⁶s⁻¹ (except Hb St. Mandé which displayed only the faster phase). Study of the mutated subunits of HbJ Mexico (α subunit) and Hb Hôtel Dieu (β subunit) showed that they convert exponentially to the stable deoxy state after photodeligation at the same rates as the corresponding subunits of normal Hb: 1.1 × 10⁶s⁻¹ (α) and 0.3 × 10⁶s⁻¹ (β). The results indicate that there is no direct correlation between the kinetics of spectral relaxation in the time range studied and the oxygenation properties for these hemoglobins. However, there is some indication that the kinetics are dependent upon the region of mutation.