Temperature-Driven Changeover in the Electron-Transfer Mechanism of a Thermophilic Plastocyanin

We have previously reported on how

José Luis Olloqui-Sariego

2014

Scholarcy highlights

  • Phormidium laminosum adsorbed on 1,ω-alkanedithiol self-assembled monolayers deposited on gold have been investigated
  • Among them stand out the analysis of the effects of protein-electrode distance, temperature or solution viscosity on the electron transfer rate constant. These studies have revealed two distinct kinetic regimes, in which ET rates are either independent or exponentially dependent on the protein-electrode distance. This last regime is well described by a non-adiabatic electron transfer mechanism, where the ET rate is controlled by the electron tunneling frequency at the top of the activation barrier
  • The nature of the rate-limiting event is more ambiguous for the distance-independent kinetic regime, for which two alternatives have been purported in the literature
  • Each kinetic regime can be further characterized by a distinct dependence of the ET rate constant with temperature and solution viscosity, though temperature or viscosity driven mechanism transitions have not yet been reported for metallo-proteins
  • We provide clear experimental evidence of a changeover in the electron transfer regime along a thermal scan when Pc-PhoWT is immobilized on a 1,11-undecanedithiol monolayer
  • Adsorbed on the n = 11 SAM, use was made of the distinct sensitivity of the non-adiabatic and distance-independent kinetic regimes to changes in the solution viscosity η
  • This transition results from the interplay between different contributions to the observed electron transfer rate, and our previous analysis helps to identify some physical prerequisites, such as the necessary difference in activation enthalpy between the two kinetic regimes or the importance of an adequate choice of the tunneling distance, to observe similar transitions for other redox proteins

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