Protein Electronic Energy Transport Levels Derived from High-Sensitivity Near-UV and Constant Final State Yield...

Area of Science:

• Surface Science
• Biophysics
• Materials Science

Background:

• Proteins are promising for molecular electronics but require understanding their electronic properties for device applications.
• Traditional methods like UV Photoemission Spectroscopy (UPS) can denature proteins, hindering accurate measurements of electrode-protein interfaces.

Purpose of the Study:

• To develop and validate a non-denaturing method for characterizing the electronic properties of protein-electrode interfaces.
• To investigate the role of the redox center in protein charge transport using advanced spectroscopy.

Main Methods:

• High-sensitivity soft UV photoemission spectroscopy (HS-UPS) combined with Constant Final State Yield Spectroscopy (CFS-YS).
• Measurement of frontier orbital energy levels (HOMO onset) for Azurin and its Apo-form on gold substrates.
• Comparison of HS-UPS/CFS-YS results with Photoelectron Yield Spectroscopy (PYS).

Main Results:

• HS-UPS/CFS-YS successfully measured protein energetics without causing denaturation.
• A significant difference (≈0.2 eV) in HOMO onset energy was observed between Azurin and its Apo-form, highlighting the Cu redox center's importance.
• Experimental results from HS-UPS/CFS-YS showed strong agreement with PYS measurements.

Conclusions:

• Combined HS-UPS and CFS-YS offer a powerful, non-denaturing tool for characterizing protein-electrode interfaces.
• This technique enables precise mapping of interface energetics, crucial for designing molecular electronic devices.
• The findings facilitate the optimization of protein-based devices for targeted electronic properties and novel applications.