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Electron tunneling in azurin: the coupling across a beta-sheet
J J Regan1, A J Di Bilio, R Langen
1Department of Physics, University of California at San Diego, La Jolla 92093-0319, USA.
Chemistry & Biology
|July 1, 1995
Summary
Electron transfer through proteins like azurin can be visualized as "tubes" of covalent and hydrogen bonds. Hydrogen bonds are crucial for interference effects in beta-sheet structures, influencing electron flow control.
Area of Science:
- Biophysics
- Biochemistry
- Protein Science
Background:
- Investigating electron flow control in biological molecules.
- Standard theories of electron transfer (ET) rely on electronic coupling and nuclear factors.
- Examining the role of protein structure (secondary and tertiary) in tunneling coupling.
Purpose of the Study:
- Evaluate contributions of covalent bonds, hydrogen bonds, and through-space jumps in coupling.
- Analyze electron tunneling through beta-strands and beta-sheets in azurin.
- Understand the mechanisms controlling electron flow in biological systems.
Main Methods:
- Analysis of four distant electronic couplings in azurin.
- Utilized a copper atom and a Ru(bpy)2(im) complex attached to histidine.
- Experimental setups involved beta-strand and beta-sheet intervening media.
Main Results:
- Electron tunneling in proteins can be modeled as ET 'tubes' formed by covalent and hydrogen bonds.
- Identified trivial and crucial inter-tube interference effects.
- Demonstrated that hydrogen bonds are as significant as covalent bonds in beta-sheet coupling.
Conclusions:
- Electron tunneling pathways in proteins can be described as specific bond-based 'tubes'.
- Hydrogen bonds play a critical role in inter-tube interference, particularly in beta-sheet structures.
- This provides a new framework for understanding and controlling electron flow in proteins.
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