| Abstract: | When oxygen binds to one of the subunits of hemoglobin, the oxygen affinity of the other subunits is enhanced. This cooperative interaction of the subunits is initiated by the movement of the heme plane toward the proximal side when oxygen binds to the heme. This motion is transmitted to the surface of the globin through a “reaction channel” consisting of a group of atoms whose motion is well correlated. Considering the detailed geometry and X-ray diffraction data of the mean square displacement of the atoms surrounding the heme, a simple model for the heme plane oscillations is developed. Using this model, the natural frequency of oscillations is shown to be ≈5 × 1011 Hz. This result, along with the recent experimental data on the kinetics of the conformational changes of the heme, points to the possibility of radiation influencing the oxygen affinity of hemoglobin. If such an effect exists, it is likely that the oxygen affinity will be enhanced by the radiation. |
