SITE-SPECIFIC MODIFICATION OF ALPHA-HELICAL PEPTIDES WITH ELECTRON DONORS AND ACCEPTORS

摘要

We have prepared a histidine containing monomeric alpha-helical peptide, ETH6 (A(2)KA(4)KA(2)HA(6)HA(4)KA(4)K) in order to study long-range electron transfer (ET). This peptide was site-specifically labeled with a ruthenium (donor) at one histidine and a second ruthenium (acceptor) at a second histidine located on the same peptide. Both the unlabeled peptide and the singly labeled peptide-metal complex, Ru(bpy)(2)(im)(His)-ETH6, were shown to form stable monomeric alpha-helical structures as determined by circular dichroism. Ru(NH3)(4)(py) was coupled to Ru(bpy)(2)(im)(His)-ETH6, forming a Ru(bpy)(2)(im)(His)-ETH6-(His)Ru(NH3)(4)(py) donor-acceptor complex. The synthesis and characterization of these peptides provide an entry into a series of molecules that are ideally suited to evaluate pathway differences such as H-bond mediated versus backbone-coupled long-range ET in protein alpha-helices. [References: 37]