Dynamical Effects in Protein Electrochemistry.

Area of Science:

• Biophysics
• Electrochemistry
• Physical Chemistry

Background:

• Electron transfer from electrodes to immobilized proteins exhibits distance-dependent and distance-independent regimes.
• The distance-independent regime is attributed to friction-controlled electron transfer, but existing theories struggle to match experimental relaxation times.

Purpose of the Study:

• To resolve the discrepancy between experimental observations and theoretical expectations for friction-controlled electron transfer rates.
• To develop a new model that incorporates protein dynamics to accurately describe experimental data.

Main Methods:

• Electrochemical measurements of electron transfer rates at varying protein immobilization distances.
• Theoretical modeling incorporating protein low-frequency oscillations and translational motions.
• Analysis of rate constants in relation to electrode-protein distance and medium relaxation times.

Main Results:

• A new model including protein oscillations in a harmonic potential successfully explains experimental electron transfer rates.
• Protein translational motions introduce a new timescale affecting the pre-exponential factor of the rate constant.
• The model extends the understanding of friction-controlled kinetics and predicts a significant temperature dependence for the enthalpy of activation.

Conclusions:

• Protein low-frequency oscillations are crucial for understanding friction-controlled electron transfer.
• The developed model reconciles experimental findings with theoretical predictions, improving the accuracy of electron transfer rate calculations.
• This work highlights the importance of considering protein dynamics in electrochemical systems and predicts novel thermodynamic properties.