INVESTIGADORES
MURGIDA Daniel Horacio
congresos y reuniones científicas
Título:
Electric Field Modulation of Electron Transfer Dynamics in Heme and Copper Proteins
Autor/es:
MURGIDA, D. H.
Lugar:
Viena
Reunión:
Conferencia; 216th Electrochemical Society Meeting; 2009
Resumen:
Electron transfer (ET) chains involved in
photosynthesis and aerobic respiration take place at the level of biological
membranes where protein complexes exert their function under the influence of
strong electric fields. Here we report a study on the influence of these fields
on the structure and ET dynamics of different heme soluble proteins (cyt-c;
cyt-b562, cyt-c6, iso-cyt-c) that act as electron
shuttles in photosynthetic and respiratory chains of different organisms. The
proteins are immobilized on nanostructured Ag electrodes coated with biomimetic
films that are designed depending on the surface properties of each redox
protein.1,2 Structure, ET kinetics and protein dynamics are studied
simultaneously by using two-colors time-resolved surface-enhanced resonance
Raman (TR-SERR) spectroelectrochemistry.2 The atomistic
interpretation of the experiments is guided by molecular dynamics (MD) simulations
and electron pathways calculations of the biomimetic complexes. This powerful
combination of theoretical and experimental methods provides a detailed and
consistent picture of the interfacial ET mechanisms.3 In each case
it is concluded that the overall ET rates are determined by an interplay of
protein dynamics and tunneling probabilities at the different conformations
along the dynamics. In turn, protein dynamics is strongly modulated by the
interfacial electric field, as demonstrated by TR-SERR experiments and MD
simulations performed under different conditions. It is also shown that
sufficiently strong electric fields are able to induce reversible structural
changes of the ferric proteins in the complexes, which produce a dramatic
down-shift of the reduction potentials.
For the natural partner protein of most
cytochromes, i.e. the CuA center of cyt-c oxidase, local and global electrostatics
are also shown to be crucial in modulating reduction potentials, reorganization
energies and crucial structural features.
Based on these results it
is hypothesized that transmembrane potentials play a regulatory role in
respiration and photosynthesis via a feedback inhibition mechanism.