Free radical formation under γ-irradiation: an EPR investigation of N-carbamyl-DL-α-amino-N-butyric acid, adipamide, and N-carbamyl-L-glutamic acid

Electron paramagnetic resonance (EPR) spectroscopy is used to investigate radicals generated in N-carbamyl-DL-α-amino-n-butyric acid (NCABA), adipamide (ADPM), and N-carbamyl-L-glutamic acid (NCLGA) after γ-irradiation at room temperature. The experimental spectra show characteristic hyperfine patterns that are well reproduced by simulations. For NCABA, the spectrum with g = 1.9990 ± 0.0005 is attributed mainly to the –CH2ĊH2NH– radical, with a smaller contribution from –NHCON˙H–. The ADPM spectrum, spanning 12.6 mT, is explained by the –CH2ĊHNH2– radical, with a g-value of 2.0035 ± 0.0005. The hyperfine structure originates from the α-proton, the amide nitrogen nucleus (aN = 0.95 mT), and the two amidic protons (aNH2 = 0.34 mT). In NCLGA, an α-carbon-centered captodative radical –COOHCH2ĊHCH(NHCONH2)COOH– is identified with g = 2.0062 ± 0.0005, aα = 3.50 mT, and aN = 0.39 mT. These findings demonstrate that γ-irradiation produces well-defined radicals in NCABA, ADPM, and NCLGA, consistent with literature values.