Electron transfer in apoferritin probed by muon spin relaxation

Electron-transfer processes play a vital role in many biological phenomena, from energy storage to photosynthesis. The labelled electron method using positive muons allows such transfer processes in macromolecules, such as proteins, to be probed on a microscopic level. Here we present the results of an experiment using the labelled electron method with μSR to investigate electron-transfer processes in apoferritin. The data is well described using the Risch–Kehr model and the results suggest one dimensional, or intra-chain diffusion occurs in this system. Intra-chain diffusion rates of 10 12 rad/s have been determined.