Tryptophan to Tryptophan Hole Hopping in an Azurin Construct

Area of Science:

• Biophysical Chemistry
• Computational Chemistry
• Molecular Biophysics

Background:

• Electron transfer (ET) is fundamental to biological processes.
• Hole-hopping mechanisms accelerate ET rates, mimicking natural systems.
• Understanding ET in engineered proteins informs artificial photosynthesis.

Purpose of the Study:

• Investigate ET between tryptophan residues in a Re-azurin construct.
• Elucidate the mechanism of photochemical hole-hopping.
• Identify factors governing efficient ET for designing artificial systems.

Main Methods:

• Born-Oppenheimer quantum-mechanics/molecular mechanics/molecular dynamics (QM/MM/MD) simulations.
• Utilized UKS-DFT for accurate electronic structure calculations.
• Analyzed forward, reverse, and back ET steps within the construct.

Main Results:

• Simulations identified equilibrium and back ET between W124 and W122 residues.
• Strong electronic coupling ensures adiabatic ET, with solvation and protein dynamics influencing energy levels.
• ET probability is sensitive to the orientation and rotation of the Re(CO)3(dmp) moiety.

Conclusions:

• QM/MM/MD simulations accurately model ET in complex protein systems.
• Solvation and protein dynamics play critical roles in tuning ET efficiency.
• Insights gained are vital for designing artificial systems with accelerated hole-hopping.