Multiheme cytochromes (MHCs) are bacterial electron-transfer proteins. We show from optical spectra and calculations that some of these cytochromes probably contain occupied and unoccupied bands formed from heme π and π* orbitals that span the protein. In the fully oxidised proteins, the unoccupied π*-bands are energetically above the redox-active frontier orbitals, which according to NMR data and calculations, are formed of Fe3+ t2g and porphyrin π-orbitals. These orbitals on different hemes are electronically coupled according to EPR data and calculations, but only weakly so. We suggest a role for the heme bands in the electronic conductivity of single MHCs in bioelectronic junctions that is distinct from the role of the redox-active Fe3+ t2g and porphyrin π-orbitals in physiological electron transfer.
Original languageEnglish
Article number101556
JournalCurrent Opinion in Electrochemistry
Early online date12 Jun 2024
Publication statusE-pub ahead of print - 12 Jun 2024

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