2 research outputs found
Disentangling Electron Tunneling and Protein Dynamics of Cytochrome <i>c</i> through a Rationally Designed Surface Mutation
Nonexponential distance dependence
of the apparent electron-transfer
(ET) rate has been reported for a variety of redox proteins immobilized
on biocompatible electrodes, thus posing a physicochemical challenge
of possible physiological relevance. We have recently proposed that
this behavior may arise not only from the structural and dynamical
complexity of the redox proteins but also from their interplay with
strong electric fields present in the experimental setups and in vivo
(J. Am Chem. Soc. 2010, 132, 5769−5778). Therefore, protein dynamics are finely controlled
by the energetics of both specific contacts and the interaction between
the protein’s dipole moment and the interfacial electric fields.
In turn, protein dynamics may govern electron-transfer kinetics through
reorientation from low to high donor–acceptor electronic coupling
orientations. Here we present a combined computational and experimental
study of WT cytochrome <i>c</i> and the surface mutant K87C
adsorbed on electrodes coated with self-assembled monolayers (SAMs)
of varying thickness (i.e., variable strength of the interfacial electric
field). Replacement of the positively charged K87 by a neutral amino
acid allowed us to disentangle protein dynamics and electron tunneling
from the reaction kinetics and to rationalize the anomalous distance
dependence in terms of (at least) two populations of distinct average
electronic couplings. Thus, it was possible to recover the exponential
distance dependence expected from ET theory. These results pave the
way for gaining further insight into the parameters that control protein
electron transfer