Effect of the Electric Field Generated by the Helix Dipole on Photoinduced Intramolecular Electron Transfer in Dichromophoric α-Helical Peptides

Abstract

In this work, we have investigated the effect of the position of probe chromophores relative to the direction of the electric field generated by the helix on the rate of intramolecular electron transfer reactions. Helical oligopeptides 1 and 2 with pendant electron donor (D) and acceptor (A) chromophores differ only by the positional reversal of the donor-acceptor (DA) pair along the dipolar helix. Hence we anticipate that the alignment of the electric field in 1 against the direction of photoinduced electron transfer should induce a faster rate of electron transfer in 1 than in 2. Our observations suggest that the orientation of a donor-acceptor pair with respect to the molecular electric field generated by the helix dipole of a peptide affects the electron transfer rates in the expected manner. 21 refs., 1 fig., 1 tab.