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Helical peptides carrying a redox-active ferrocene moiety at the terminal were self-assembled on a gold surface. The long-range electron transfer from the ferrocene moiety to gold was studied by electrochemical methods. These covered the effects by the peptide dipole, the side-chains, chain lengths, molecular orientation, monolayer packing, and linkers connecting the peptides to gold. The helical peptides formed a well-organized monolayer with vertical orientation revealed by ellipsometry, infrared spectroscopy, and electrochemical blocking experiments. The electron transfer was studied by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The following interesting features were clarified: 1) the peptide dipole slightly accelerates the electron transfer of the same direction compared to the opposite case, 2) introduction of chromophores at side chains does not affect the electron transfer, 3) the distance dependence suggests a hopping mechanism with the amide groups as hopping sites 4) an electron is transferred across a few peptides if the peptide backbones are close to each other, 5) the electron transfer is associated with a certain molecular motion, and 6) substitution of an aromatic linker for an alkyl linker remarkably accelerates the electron transfer, but modification of electronic level of the aromatic linker does not affect the electron transfer. [ABSTRACT FROM AUTHOR]