High-Temperature Electrochemistry of a Solvent-Free Myoglobin Melt

The electrochemical responses from a hybrid biofluid comprising lithium hexafluorophosphate (LiPF₆) dispersed in a solvent-free myoglobin melt are investigated over an extreme temperature range (30-150°C). Incorporation of LiPF₆ resulted in an approximately 20-fold increase in the conductivity of the biofluid across the entire temperature range. A polaron-type mechanism involving electron hopping from heme-to-heme centers of myoglobin, accompanied by extrinsic Li counter-ion movement, is proposed for the charge-transport kinetics in the solvent-free melt. Significantly, the redox signature of the heme prosthetic group varied systematically and reversibly with temperature, which was consistent with hyperthermophilic unfolding/refolding of the protein structure.