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Universal mechanism for breaking amide bonds by ionizing radiation.
Phillip S Johnson1, Peter L Cook, Xiaosong Liu
1Department of Physics, University of Wisconsin-Madison 1150 University Ave., Madison, Wisconsin 53706, USA.
The Journal of Chemical Physics
|August 3, 2011
Summary
UV and soft X-ray irradiation of amides causes photodissociation. This process, studied using X-ray absorption spectroscopy, reveals a universal signature involving oxygen loss and hydrogen migration, forming imines or nitriles.
Area of Science:
- Chemical Physics
- Materials Science
- Biochemistry
Background:
- The amide bond is fundamental in peptides, proteins, and synthetic polymers like nylon.
- Understanding amide bond photodissociation is crucial for materials science and biochemistry.
Purpose of the Study:
- To investigate the photodissociation mechanism of the amide bond induced by UV and soft X-rays.
- To identify universal spectroscopic signatures of amide bond cleavage across various amide types.
Main Methods:
- X-ray absorption spectroscopy (XAS) was employed at the Carbon (C), Nitrogen (N), and Oxygen (O) 1s electronic edges.
- Spectra were analyzed to identify changes in electronic structure upon irradiation.
Main Results:
- A universal photodissociation signature was observed for diverse amides, including peptides and polyamides.
- N 1s edge spectra showed a characteristic 1.1 eV splitting of π* peaks, indicating imine and nitrile formation.
- O 1s edge spectra revealed intensity reduction, signifying oxygen atom loss.
Conclusions:
- The study elucidates a common photodissociation pathway involving O atom release and H atom migration to form imines or nitriles.
- The findings provide a spectroscopic basis for understanding amide bond degradation under UV and soft X-ray irradiation.
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Acid-catalyzed hydrolysis:
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