Preference of oxygenation between alpha and beta subunits of haemoglobin. Results of multidimensional spectroscopic...

The distribution of oxygen between the subunits of haemoglobin was studied spectrophotometrically. The difficulty in discriminating the spectral changes upon oxygen binding to the alpha or beta subunit can be surmounted by means of multidimensional spectroscopic observations and a correlation analysis of the data. M-type abnormal haemoglobins are used as a control against normal haemoglobin because only one type of its subunits can bind oxygen. A multidimensional spectroscopic measuring system, which has been developed in our laboratory, makes it possible to carry out simultaneous and continuous acquisition of a set of spectroscopic data at several wavelengths on one sample solution during the course of increasing or decreasing the partial pressure of oxygen. The data-storing function of a magnetic disk memory provides enough precision for a rigorous investigation of the correlation of oxygen equilibrium curves measured at several wavelengths. No chemical modification to enhance the spectral difference between subunits is necessary. In conclusion, by detecting slight differences between the oxygenation-sensitive bands of alpha and beta subunits, the beta subunits are found to have a higher affinity for oxygen than the alpha subunits.