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:
<!-- @page { size: 8.5in 11in; margin: 0.79in } P { margin-bottom: 0.08in } --> 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.