Preparation and functions of self-assembled monolayers of helix peptides

Self-assembled monolayers (SAMs) of helix peptides oriented vertically to a gold surface were prepared. Negative surface potentials of a few hundred millivolts were observed for the helix peptide SAMs when they were immobilized on gold through the N terminal of the peptides. However, positive surface potentials were generated in the helix peptide SAMs when the N terminal of the peptides was directed the opposite way. The large dipole moment of the helical peptide was thought to be the major factor for generation of the surface potential. The effect of the dipole moment on the electron transfer through the helix peptide SAMs was investigated. Photocurrent generation by photoexcitation of the N-ethylcarbazolyl group of the peptide SAMs was accelerated by the dipole moment directed toward the gold substrate. Helical peptides were thus shown to be a suitable medium for electron transfer.