Myoglobin oxygen dissociation by multiwavelength spectroscopy

Kenneth A. Schenkman 1 , David R. Marble 2 , David H. Burns 3 , and Eric O. Feigl 2 1 Department of Pediatrics, University of Wisconsin, Madison, Wisconsin 53792; 2 Departments of Bioengineering and Physiology, University of Washington, Seattle, Washington 98195; and 3 Department of Chemistry, McGill University, Montreal, Quebec, Canada H3A 2K6 Received 13 March 1996; accepted in final form 21 August 1996. Schenkman, Kenneth A., David R. Marble, David H. Burns, and Eric O. Feigl. Myoglobin oxygen dissociation by multiwavelength spectroscopy. J. Appl. Physiol. 82(1): 86-92, 1997. 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°C, at pH 7.0. In addition, dissociation curves were determined at 37°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 P O 2 at which myoglobin is half-saturated with O 2 (P 50 ) was determined to be 2.39 Torr at pH 7.0 and 37°C. The myoglobin dissociation curve was well fit by the Hill equation [saturation = P O 2 /(P O 2 + P 50 )]. equilibration; metmyoglobin; least squares analysis; second derivative 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society