Patent ID: 7223847

Claim:
A method for producing a cobalt-protein complex comprising: the step a) of preparing a solution including Co 2+ ions, a protein, and HEPES, and having a pH of not less than 8.0 and not more than 8.8; and a step b) of adding an oxidizing agent to the solution and thereby making the protein contain particles composed of cobalt, wherein the protein is apoferritin, the concentration of the Co 2+ ions is not less than 2.5 mM and not more than 5.0 mM, the pH of the solution is adjusted to be not less than 8.0 and not more than 8.8 when the concentration of the Co 2+ ions is not less than 2.5 mM and not more than 3.5 mM, the pH of the solution is adjusted to be not less than 8.0 and not more than 8.4 when the concentration of the Co 2+ ions is more than 3.5 mM and not more than 4.0 mM, and the pH of the solution is adjusted to be not less than 8.0 and not more than 8.2 when the concentration of the Co 2+ ions is more than 4.0 mM and not more than 5.0 mM.