Long-distance electron tunneling in proteins: A new challenge for time-resolved spectroscopy

Long-distance electron tunneling is a fundamental process which is involved in energy generation in cells. The tunneling occurs between the metal centers in the respiratory enzymes, typically over distances up to 20 or 30 such distances, the tunneling time—i.e., the time during which an electron passes through the body of the protein molecule from one metal center to another—is of the order of 10 fs. Here the process of electron tunneling in proteins is reviewed, and a possibility of experimental observation of real-time electron tunneling in a single protein molecule is discussed.