Electron paramagnetic resonance study of free radicals in γ-irradiated L-glutamine and L-glutamine-t-butyl ester hydrochloride

Abstract

Electron paramagnetic resonance (EPR) spectra of γ -irradiated single crystals of l-glutamine (LG) and l-glutamine-t-butyl ester hydrochloride (LGBESHCI) powders were studied and analyzed for different orientations of the crystals in the magnetic field, after γ -irradiation. The spectra were observed to be independent of temperature down to 130 K. The hyperfine interaction tensors for one α proton and two β protons of radical have been determined at 295 K. An analysis of the EPR of γ -irradiated single crystals of LG and LGBESHCI powders shows that the paramagnetic species produced by the radiation damage is CH 2Ċ H. The g values of the radical and the hyperfine structure constants of the free electron with nearby protons and 14 N nucleus were determined. The results were found to be in good agreement with the existing literature data.

An Electron Paramagnetic Resonance (EPR) spectroscopy study on the γ-irradiation sterilization of the pharmaceutical excipient l-histidine: Regeneration of the radicals in solution

“…The identity of the main radical species generated by irradiation was confirmed by EPR analysis of both the L-his powder and the single crystal. The irradiation products of numerous amino acids have been investigated previously by EPR in the solid state (Aydin, 2010;Dicle et al, 2015;Karabulut and Yıldırım, 2015), but here the reactivities of the radicals following dissolution were also evaluated by means of spin-trapping EPR experiments (Davies, 2016). While studies involving the spin trapping of radicals formed in the solid state have been previously reported for several organic compounds, including amino acids (Kuwabara et al, 1981;Lagercrantz and Forschult, 1968;Makino and Riesz, 1982;Minegishi et al, 1980;Talbi et al, 2004) we are not aware of previous reports of the regeneration and trapping of amino acid radicals in solution upon addition of the trapping agent many minutes after dissolution of an irradiated powder.…”