Designed azurins show lower reorganization free energies for intraprotein electron transfer

Ole Farver, Nicholas M. Marshall, Scot Wherland, Yi Lu, Israel Pecht

Research output: Contribution to journalArticlepeer-review


Low reorganization free energies are necessary for fast electron transfer (ET) reactions. Hence, rational design of redox proteins with lower reorganization free energies has been a long-standing challenge, promising to yield a deeper understanding of the underlying principles of ET reactivity and to enable potential applications in different energy conversion systems. Herein we report studies of the intramolecular ET from pulse radiolytically produced disulfide radicals to Cu(II) in rationally designed azurin mutants. In these mutants, the copper coordination sphere has beenfine-tuned to span awide range of reduction potentials while leaving the metal binding site effectively undisrupted. We find that the reorganization free energies of ET within the mutants are indeed lower than that of WT azurin, increasing the intramolecular ET rate constants almost 10-fold: changes that are correlated with increased flexibility of their copper sites. Moreover, the lower reorganization free energy results in the ET rate constants reaching a maximum value at higher driving forces, as predicted by the Marcus theory.

Original languageEnglish (US)
Pages (from-to)10536-10540
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number26
StatePublished - Jun 25 2013


  • Blue copper
  • Cupredoxin
  • Marcus inverted region
  • Reorganization energy
  • Type 1 copper

ASJC Scopus subject areas

  • General

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