Catalytic Turnover of [FeFe]-Hydrogenase Based on Single Molecule Imaging

Christopher Madden, Michael D. Vaughn, Ismael Díez-Pérez, Katherine A. Brown, Paul W. King, Devens Gust, Ana L. Moore, Thomas A. Moore

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157 Scopus Citations


Hydrogenases catalyze the interconversion of protons and hydrogen according to the reversible reaction: 2H + + 2e - H 2 while using only the earth-abundant metals nickel and/or iron for catalysis. Due to their high activity for proton reduction and the technological significance of the H +/H 2 half reaction, it is important to characterize the catalytic activity of [FeFe]-hydrogenases using both biochemical and electrochemical techniques. Following a detailed electrochemical and photoelectrochemical study of an [FeFe]-hydrogenase from Clostridium acetobutylicum (CaHydA), we now report electrochemical and single-molecule imaging studies carried out on a catalytically active hydrogenase preparation. The enzyme CaHydA, a homologue (70% identity) of the [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, was adsorbed to a negatively charged, self-assembled monolayer (SAM) for investigation by electrochemical scanning tunneling microscopy (EC-STM) techniques and macroscopic electrochemical measurements. The EC-STM imaging revealed uniform surface coverage with sufficient stability to undergo repeated scanning with a STM tip as well as other electrochemical investigations. Cyclic voltammetry yielded a characteristic cathodic hydrogen production signal when the potential was scanned sufficiently negative. The direct observation of the single enzyme distribution on the Au-SAM surface coupled with macroscopic electrochemical measurements obtained from the same electrode allowed the evaluation of a turnover frequency (TOF) as a function of potential for single [FeFe]-hydrogenase molecules.

Original languageAmerican English
Pages (from-to)1577-1582
Number of pages6
JournalJournal of the American Chemical Society
Issue number3
StatePublished - 2012

NREL Publication Number

  • NREL/JA-2700-52561


  • electrochemical
  • FeFe
  • hydrogenase
  • photoelectrochemical


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