The formation and characterization of Selenocysteine (SeCys) Self-assembly monolayers (SAMs) was studied. It was found that SeCys SAMs revealed ion-gate response for the electron-transfer of Fe(CN)(6)(4-/3-) probe ion in the presence of Cu(2+) or Pb(2+). The ion-gate response of SeCys SAMs resulted from the fact that the interaction between SeCys SAMs and Cu(2+) (Pb(2+)), including the coordination and the electrostatic interaction, changed the conformation of SeCys SAMs. (C) 2011 Elsevier B.V. All rights reserved.