ESR and ENDOR studies of x-irradiated l -proline monohydrate and l -thioproline single crystals

Radicals with extended lifetimes at room temperature, and formed by x irradiation of the parent compounds, were studied by ESR and ENDOR spectroscopy. The radicals’ characteristics in each case are similar and include significant couplings to one α proton (Aiso = −54.8 MHz for proline and −51.0 MHz for thioproline), and one β proton (Aiso = 64.0 MHz for proline and 53.8 MHz for thioproline). Further analysis of the results indicates the radicals to result from a reaction similar to deamination, evidently originating with electron capture by the respective parents.