Banding of Hæm to Protein in Hæmoglobin and Myoglobin

Abstract

THE equation deduced by Drs. Falk, Phillips and Perrin would seem applicable only when interaction between the ‘metal’ and ligand would be high, for example, in the hæm compounds which have reacted with oxygen or carbon monoxide. If the interaction were low, as it seems to be in the hæmatin compounds on which my experiments were performed, where dissociations appear to be simple (for example, in hydroxide formation) and the linkages ‘essentially ionic’, then the second and third terms on the right-hand side of the equation could be discarded. My interpretation assumed this, and that removal of the insoluble hæmatin, with polymerization and loss of absorbance, ‘indicated’ the dissociation of the bonding group of the protein. It was also assumed that over the range of hydrogen ion concentration studied, contributions to the absorbance from linkages to the hæmatin propionate side-chains would be low. The latter opinion now appears confirmed, since the dissociation of ferriætiomyoglobin (prepared from ætiohæmin, with no carboxyl groups) apparently follows the theoretical curve for an acid group with pK = 4.95 (at 21°, µ = 0.05)¹.