(53e) Single Molecule Study of Charge Transport in Redox Active Biomolecules

Charge transport in single molecules is essential for energy transfer in biological systems and forms the fundamental basis for molecular electronics. Recent experimental and theoretical work has focused on charge transport in synthetic Ï€-conjugated molecules via electron tunneling. However, charge transport in sequence-defined biomolecules capable of hierarchical assembly remains largely untapped. A major goal is to understand the relationship between molecular design and intrachain charge transport mechanisms in synthetic and biological materials. In this talk, I will present recent work on single molecule charge transport in oligopeptides containing redox-active amino acid side chains (tyrosine, tryptophan, histidine, and DOPA). Extremely high conductance (ranging between 10^-2 G₀ to 10^-1 G₀) was observed for certain sequence-defined oligopeptides using scanning tunneling microscopy-break junction measurements (STM-BJ). The role of the redox-active group in charge transport was explored, suggesting a charge transport mechanism based on proton-coupled electron transfer, which has been observed in Photosystem II. In addition, the relationship between molecular design and conductance at the single molecule level was investigated. Overall, our work provides insights into charge transport in biological redox macromolecular machines and provides evidence of long-range charge transport in biomolecules.