Orientation-dependent electron transport in a single redox protein

Area of Science:

• Biophysics
• Molecular Engineering
• Nanotechnology

Background:

• Cytochrome b(562) is a redox-active protein crucial for electron transfer.
• Controlling protein orientation and electrical contact is vital for bioelectronic applications.

Purpose of the Study:

• To engineer cytochrome b(562) for controlled surface binding and electrical contacting.
• To investigate the influence of protein orientation and heme placement on electron transfer.

Main Methods:

• Site-directed mutagenesis to introduce cysteine pairs for thiol group functionalization.
• Scanning Tunneling Microscopy (STM) for imaging and current-voltage/current-distance measurements.
• Electrical characterization of engineered proteins on gold surfaces.

Main Results:

• Engineered proteins showed controlled orientation on gold via one thiol group, maintaining native structure.
• Stable electrical contact was achieved through a second thiol group.
• Protein conductance varied based on thiol placement, with values ranging from 1.95 × 10(-5)G(0) to 3.57 × 10(-5)G(0).
• Engineered proteins exhibited significantly higher conductance than wild-type cytochrome b(562).

Conclusions:

• Demonstrated controllable orientation and electrical contacting of an engineered electron transfer protein on gold.
• Showcased the influence of protein structure and heme localization on electron transfer properties.
• Established a foundation for integrating functional proteins into electronic devices.