Physical and Chemical Studies on Ceruloplasmin. Ii. Molecular Oxygen and the Blue Color of Ceruloplasmin.

In their description of the isolation and properties of ceruloplasmin, Holmberg and Laurel1 (1) noted that this intensely blue copper-protein could be decolorized by reducing agents such as ascorbic acid. Although the decoloriaation was “. . . completely reversible in the presence of oxygen, attempts to (restore blue color by oxidation) with potassium ferricyanide were not successful.” They wondered, therefore, whether the reversible decolorization was due to successive reduction and oxidation of the copper ions in ceruloplasmin, or to a reversible oxygenation of the kind to which the deep blue color of hemocyanin has been ascribed. In this communication, we report experiments from which we have concluded that the blue color of ceruloplasmin is not dependent on the presence of molecular oxygen in the protein molecule.