Electro-chemical transduction in elastic protein-based polymers: a model for an energy conversion step of oxidative phosphorylation.

A pair of functional moieties, the carboxyl of an aspartic acid (Asp, D) residue and an N-methyl nicotinamide (NMeN) formed on amide linkage to the epsilon-amino group of the lysine (Lys, K) residue, are coupled to perform energy conversion by means of controlling the transition temperature, Tt, of a common hydrophobic folding and assembly domain within the polytricosapeptide, poly[GDGFP GVGVP GVGVP GFGVP GVGVP GVGK(NMeN)P]. The input of electrochemical energy in the form of the reduction of nicotinamide results in a reduction-induced increase in pKa by 2.5 pH units which represents the performance of the chemical work of picking up a proton. The primary structure and the structures of the oxidized and reduced states are verified by two-dimensional nuclear magnetic resonance. Thus electrochemical transduction, the conversion of electrochemical energy into chemical energy, has been demonstrated for the first time in a designed, synthetic protein-based polymer.