Open AccessELECTRON SPIN RESONANCE OF IRRADIATED SINGLE CRYSTALS OF L-PHENYLALANINE-HCL
Author(s) -
Edwin L. Fasanella,
Walter Gordy
Publication year - 1969
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.64.1.1
Subject(s) - electron paramagnetic resonance , radical , methylene , hyperfine structure , chemistry , phenylalanine , proton , crystallography , carbon fibers , irradiation , photochemistry , spin (aerodynamics) , resonance (particle physics) , ring (chemistry) , nuclear magnetic resonance , amino acid , materials science , medicinal chemistry , organic chemistry , atomic physics , physics , biochemistry , quantum mechanics , composite number , nuclear physics , composite material , thermodynamics
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.