INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Molecular Basis of Coupled Protein and Electron Transfer Dynamics of Cytochrome c in Biomimetic Complexes.
Autor/es:
MARCELO A MARTI
Lugar:
Universidad Nacional del Litoral Santa Fe, Argentina
Reunión:
Congreso; Cuarto Workshop de Química Bioinorgánica Aspectos estructurales y funcionales de sistemas bioinorgánicos estudiados mediante métodos espectroscópicos, de cálculo, y sistemas modelo; 2010
Institución organizadora:
Universidad Nacional del Litoral Santa Fe, Argentina
Resumen:
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Direct
electron transfer (ET) of redox proteins immobilized on biomimetic or
biocompatible electrodes represents an active field of fundamental
and applied research. In this context, several groups have reported
for a variety of proteins unexpected distance-dependencies of the ET
rate, whose origin remains largely speculative and controversial, but
appears to be a quite general phenomenon. Here we have employed
molecular dynamics (MD) simulations and electron pathway analyses to
study the ET properties of cytochrome c (Cyt) electrostatically
immobilized on Au coated by carboxyl-terminated alkylthiols. The MD
simulations and concomitant binding energy calculations allow
identification of preferred binding configurations of the oxidized
and reduced Cyt which are established via different lysine residues
and, thus, correspond to different orientations and dipole moments.
Calculations of the electronic coupling matrices for the various
Cyt/SAM complexes indicate that the thermodynamically preferred
protein orientations do not coincide with the orientations of optimum
coupling. These findings demonstrate that the ET of the immobilized
Cyt is controlled by an interplay between protein dynamics and
tunneling probabilities. Protein dynamics exerts two level of tuning
on the electronic coupling via reorientation (coarse) and low
amplitude thermal fluctuations (fine). Upon operating the Au support
as an electrode, electric-field dependent alignment of the protein
dipole moment becomes an additional determinant for the protein
dynamics and thus for the overall ET rate. The present results
provide a consistent molecular description of previous
(spectro)electrochemical data and allow conclusions concerning the
coupling of protein dynamics and ET of Cyt in physiological
complexes.