Universal mechanism for breaking amide bonds by ionizing radiation

作者：Johnson Phillip S; Cook Peter L; Liu Xiaosong; Yang Wanli; Bai Yiqun; Abbott Nicholas L; Himpsel F J^*

来源：Journal of Chemical Physics, 2011, 135(4): 044702.

DOI：10.1063/1.3613638

• biochemistry
• molecular biophysics
• photodissociation
• polymers
• proteins
• X-ray absorption spectra

The photodissociation of the amide bond by UV light and soft x-rays is investigated by x-ray absorption spectroscopy at the C, N, and O 1s edges. Irradiation leaves a clear and universal signature for a wide variety of amides, ranging from oligopeptides to large proteins and synthetic polyamides, such as nylon. As the pi* peak of the amide bond shrinks, two new pi* peaks appear at the N 1s edge with a characteristic splitting of 1.1 eV. An additional characteristic is the overall intensity reduction of both the pi* and sigma* features at the O 1s edge, which indicates loss of oxygen. The spectroscopic results are consistent with the release of the O atom from the amide bond, followed by the migration of the H atom from the N to one of its two C neighbors. Migration to the carbonyl C leads to an imine, and migration to the C-alpha of the amino acid residue leads to a nitrile. Imine and nitrile produce the two characteristic pi* transitions at the N 1s edge. A variety of other models is considered and tested against the N 1s spectra of reference compounds.

• 出版日期2011-7-28