The heme protein cytochrome c acts as an electron carrier at the mitochondrial-membrane interface and thus exerts its function under the influence of strong electric fields. To assess possible consequences of electric fields on the redox processes of cytochrome c, the protein can be immobilized to self-assembled monolayers on electrodes and studied by surface-enhanced resonance Raman spectroscopy. Such model systems may mimic some essential features of biological interfaces including local electric field strengths. It is shown that physiologically relevant electric field strengths can effectively modulate the electron-transfer dynamics and induce conformational transitions.