Self-assembled monolayers were designed as model systems for the investigation of electron transfer mediated by peptide chains. A thiol derivative containing a cysteamine linker, four glycine residues and a ferrocene head group-Fc-(CO)-(Gly)(4)-NH-(CH2)(2)-SH, was synthesized and used for preparation of monolayer assemblies. Electrochemical methods were employed to measure the electron transfer rates through one-component oligoglycine monolayers and through mixed monolayers with oligoglycine molecules (0.2-0.5%) embedded in the alkanethiol matrix. The standard rate constant for electron tunneling through the pure oligolglycine monolayer (821 +/- 78 s(-1)) is larger than that through the mixed monolayer with alkanethiols as the main component (36 +/- 7 s(-1)) and larger than for the corresponding alkanethiol monolayer (12 s-1). (C) 2003 Elsevier Science B.V. All rights reserved.