Removal of cadmium(II) from crystallized ferritin

The cadmium content of crystallized horse spleen ferritin, usually about 2% by weight without special treatment, can be substantially decreased by prolonged dialysis against certain chelating agents, chaotropic ions, or weakly reducing anions. For example, neutral bisulphite buffer (2M) removed 95% of the bound cadmium of crystallization without affecting the iron content, and may thus be valuable for preparing "metal-free" holoferritin for physical-chemical studies.