“…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.…”