INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Direct Observation of Protein Dynamics at Biomimetic Electrochemical Interfaces
Autor/es:
MURGIDA, D.H.
Lugar:
Sevilla, España
Reunión:
Congreso; 59th Annual Meeting of the International Society of Electrochemistry; 2008
Resumen:
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Heterogeneous electron transfer of proteins
at biomimetic interfaces is characterized by unusual distance
dependences of the electron transfer rates, whose origin has been elusive and
controversial. Using a two colours time-resolved surface-enhanced resonance
Raman spectroelectrochemical approach we have been able to monitor
simultaneously and in real time the structure, electron transfer kinetics and configurational
fluctuations of heme proteins immobilized on SAM-coated electrodes. It is shown
that the overall electron transfer kinetics is determined by protein dynamics
rather than by tunnelling probabilities. Protein dynamics, in
turn, is controlled by the interfacial electric field.
Molecular dynamics simulations and pathway
calculations show that the distribution of protein orientations in
electrostatic complexes with SAM-coated electrodes is redox state dependent.
Each orientation corresponds to a finite coupling, but significant couplings
are only observed for a very narrow range of orientations in each redox state.
Deviations larger than five degrees from the optimal orientation of the heme
with respect to the electrode surface result in a drastic decay of the
electronic coupling.
Thus, measured electron transfer rates are a
convolution of the dynamic sampling of the surface by the protein and electron tunneling probabilities at each
configuration. Implications for inter-protein electron transfer at biological membranes and for bioelectrochemistry in general will be duscussed.