Myoglobin oxygen dissociation by multiwavelength spectroscopy

Multiwavelength optical spectroscopy was used to determine the oxygen-binding characteristics for equine myoglobin. Oxygen-binding relationships as a function of oxygen tension were determined for temperatures of 10, 25, 35, 37, and 40 degrees C, at pH 7.0. In addition, dissociation curves were determined at 37 degrees C for pH 6.5, 7.0, and 7.5. Equilibration was achieved with a myoglobin solution, at the desired temperature and pH, and 16 oxygen-nitrogen gas mixtures of known oxygen fraction. Correction for the inevitable presence of metmyoglobin was made by using a three-component least squares analysis and by correcting the end point oxymyoglobin spectra for the presence of metmyoglobin. The PO2 at which myoglobin is half-saturated with O2 (P50) was determined to be 2.39 Torr at pH 7.0 and 37 degrees C. The myoglobin dissociation curve was well fit by the Hill equation [saturation = PO2/(PO2 + P50)].