Electron Spin Resonance of Irradiated Single Crystals of l-phenylalanine-HCl

Single crystals of L-phenylalanine-HCl have been observed with electron spin resonance after irradiation with a cobalt 60 γ -ray source. The predominant signals observed are from long-lived benzyl radicals. The results indicate that one form of radiation damage to proteins containing this amino acid...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1969-09, Vol.64 (1), p.1-7
Main Authors: Fasanella, Edwin L., Gordy, Walter
Format: Article
Language:English
Subjects:
Atoms
Carbon
Cobalt Isotopes
Crystallography
Crystals
Electrical couplings
Electron paramagnetic resonance
Electron Spin Resonance Spectroscopy
Free Radicals
Hydrochloric Acid
Magnetic fields
Magnetic spectroscopy
Phenylalanine - radiation effects
Physical Sciences: Physics
Physics
Protons
Radiation Effects
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Summary:Single crystals of L-phenylalanine-HCl have been observed with electron spin resonance after irradiation with a cobalt 60 γ -ray source. The predominant signals observed are from long-lived benzyl radicals. The results indicate that one form of radiation damage to proteins containing this amino acid is breakage of the carbon-carbon bond to release the benzyl radical from the polypeptide chain. Hyperfine structure due to proton couplings of the two methylene hydrogens and of the hydrogens on the ring of the benzyl radical is observed and analyzed to give the electron spin density on the various carbons. The spin density on the methylene carbon is found to be 0.71; that on carbon C(2), C(4), or C(6)is 0.17. The sum of the spin densities on C(1), C(3), and C(5)is -0.22.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.64.1.1