Electric-Field Effects on Structure and Conductance in a Cytochrome b₅₆₂ Junction.

Area of Science:

• Computational biophysics
• Molecular electronics
• Protein electrochemistry

Background:

• Experimental bias in biomolecular junctions can significantly impact protein structure and conductance.
• Large, charged proteins present computational challenges for traditional molecular-junction methods like non-equilibrium Green's function (NEGF).

Purpose of the Study:

• To develop a multiscale computational framework for studying electric field effects on large protein junctions.
• To investigate the influence of electric fields on the structure and tunneling conductance of cytochrome b562.

Main Methods:

• Combined non-equilibrium classical molecular dynamics (MD) and density functional theory (DFT) with external electric fields.
• Employed approximate transport calculations using the projection operator diabatization (POD) method.
• Differentiated electronic polarization from field-induced structural changes.

Main Results:

• Electric fields induced asymmetries in conductance and current responses relative to applied bias.
• Structural changes due to electric fields were partially offset by electronic polarization in both vacuum and aqueous solution.
• In solution, charged groups were screened by water and ions, weakening the total field effect.

Conclusions:

• The developed multiscale framework effectively analyzes electric field effects in large protein systems.
• Electric fields cause minor perturbations to protein conductance, with structural and electronic effects largely compensating.
• Environmental factors like water and ions significantly screen electric field impacts in solution.