Heme plane orientation dependent direct electron transfer of cytochrome c at SAMs/Au electrodes with different wettability.

It is proposed that direct electron transfer is dependent on the orientation of the heme plane in cytochrome c (cyt c) assembled on electrode surfaces. Orientation with the heme plane in cyt c parallel to the gold electrode surface favors the direct electron transfer, while vertical orientation of the heme plane makes the direct electron transfer difficult. A preferable electron transport pathway for cyt c is through the axial ligand (His-18) of the heme center rather than the porphyrin ring.