Carbon monoxide binding in a model of hemoglobin differs between the T and the R conformation

The ratio between carbon monoxide affinity and oxygen affinity (M) is usually assumed to have a fixed value (Haldane's law), which is about 200. However, this ratio is not a constant but depends on the level of saturation (Roughton, 1970) as well as on pH (Joels and Pugh, 1958). This means that simple procedures cannot be used to calculate the combined effects of simultaneous oxygen and carbon monoxide binding. Application of our mathematical model of hemoglobin (Zock, 1987) shows that this model can account for the above-mentioned phenomena in a straightforward way. Within the context of this mathematical model of human hemoglobin the differences in shape between oxygen equilibrium curve and carbon monoxide equilibrium curve of human hemoglobin could be readily explained by assuming that the ratio between oxygen affinity and carbon monoxide affinity differs between the T and the R conformation.