Investigation on the photo-induced de-oxygenation process of myoglobin in aqueous solution by use of fluorescence spectroscopy

A photo-induced de-oxygenation process of myoglobin (Mb) in aqueous solution was investigated by use of fluorescence spectroscopy. The spectra are characterized by the fluorescence intensity declining gradually after each scan, and the decay of fluorescence intensity being significant in each scan, which is assigned to the release of oxygen from the opening of the heme-pockets induced by illumination. More illumination will cause more release of oxygen; if the temperature of an Mb solution is increased when it is illuminated, the rate of de-oxygenation will be higher. It was found that ligand-oxygen in Fe-porphyrin could be removed from Mb by nitrogen. This indicates that the interaction between oxy-Mb and other different gases can be tested by the method of fluorescence spectroscopy. In addition, fluorescence spectroscopy can be employed to probe the energy transfer between Fe-porphyrin and tryptophan or tyrosine in Mb molecules.