Electron Transfer in Ferritin as Probed by Muon Spin Relaxation

Electron-transfer processes play a vital role in many biological phenomena, from energy storage to photosynthesis. Positive muons allow such transfer processes in macromolecules, such as proteins, to be probed on a microscopic level. We have used this probe via muon spin relaxation (μSR) to investigate electron-transfer processes in ferritin; the normal iron storage protein. Data collected at finite fields is well described using the Risch-Kehr model at all measured temperatures with inter and intra-chain diffusion rates of 109 and 1011 rad s-1 being determined respectively. The results are compared to similar measurements on other proteins.