Figure 7: Electron transfer through the ferritin protein shell. The blue dot in the cut-away view of the protein shells containing Fe(OH)2 (pink) and Co(OH)3 (purple) mineral cores represents the electron transfer centers within the ferritin shell. The model on the left indicates that the two electron transfer centers are not in contact and do not provide a pathway for electron exchange. The model on the right shows the two redox centers aligned and capable of exchanging electrons from the two mineral cores. The models only show one of several possible electron transfer centers present in each ferritin protein shell.