Monolayers of Ferrocene Peptide Conjugates

The redox-active ferrocenoyl moieties are surrounding a central H-bonded peptide core. Fcl is involved in the square helix having a right-handed twist, as observed in most p sheets, and Fc2 is involved in the twisted helix. Both helices have a pitch height of 14A. The square helix and twisted helix have an inner diameter of 3.8 A and 4.1 A, respectively. Although peptide-disulfides often exhibit unusual structural features, a supramolecular assembly as exhibited by Fc-glycylcystamine was never before observed in peptide conjugates. 

Electrochemical techniques have been used extensively to investigate the kinetics of electron transfer (ET) through self-assembled monolayers (SAMs) of molecules connected to a gold smface, leading to information about the distance dependence and the influence of solvation. 

For the pxnpose of studying the electron transfer kinetics through peptides and ordered peptide assembhes supported on a gold surface, we began to prepare a series of rigid helical ferrocenoyl-oligoprohnyl benzylesters [Fc-Pro -OR, n = 1 (R = H, 25), 2 (R = Bz, 26), 3 (R = Bz, 27), 4 (R = Bz, 28) ] and the related 

Compounds 35-41 exhibit a fully reversible one-electron oxidation wave, attributed to the oxidation of tiie Fc moiety. The oxidation potentials for 35-41 are influenced by the number of tiie attached proline residues, which is similar to the redox behavior of the related Fc-Pro -OBz (n = 1-4) (24-27). In both systems, the 

Multiple scanning experiments on this and other Fc-peptide cystamine mono-layers shows only small decreases in the signal intensity, indicating the stability of the monolayers to scanning. For a SAM of 40, over a period of 60 s, the peak current decreased by —10%, indicating that loss of the Fc label is minimal (Fig. 9). Some 

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