Lithium Formate for EPR Dosimetry (2): Secondary Radicals in X-Irradiated Crystals.

The secondary radiation-induced radicals in lithium formate monohydrate were studied using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and ENDOR-induced EPR (EIE) techniques complemented with periodic density functional theory (DFT) calculations. Single crystals of lithium formate monohydrate were X irradiated at 77 K and at room temperature. The main radicals present after irradiation at 77 K are the CO(2)(•-) radical (R1), the recently identified protonated electron-gain product, HCOOH(•-) (R2) (Krivokapić et al.

Lithium formate for EPR dosimetry: radiation-induced radical trapping at low temperatures.

Radiation-induced primary radicals in lithium formate. A material used in EPR dosimetry have been studied using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and ENDOR-Induced EPR (EIE) techniques. In this study, single crystals were X irradiated at 6-8 K and radical formation at these and higher temperatures were investigated.

Radicals in 5-methylcytosine induced by ionizing radiation. Electron magnetic resonance for structural and mechanistic analyses.

Single crystals of 5-methylcytosine hemihydrate and 5-methylcytosine hydrochloride were X-irradiated and studied at 10 K and at higher temperatures using X- and K-band EPR, ENDOR and EIE spectroscopy. In the hemihydrate crystals, four radicals were identified at 10 K, one of them being the recently reported N1-deprotonated one-electron oxidation product (Krivokapić et al., J.

Primary oxidation products of 5-methylcytosine: methyl dynamics and environmental influences.

The primary oxidation product in X-irradiated single crystals of 5-methylcytosine hemihydrate and 5-methylcytosine hydrochloride has been studied at 10 K, using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and ENDOR-induced EPR (EIE) spectroscopies. The radical is characterized by large couplings to the methyl protons and appears to be deprotonated at N1 in both crystal systems. In the hydrochloride crystal the methyl group is completely frozen at 10 K, whereas in the hemihydrate crystal it undergoes tunneling rotation.

Proton-coupled hole transfer in X-irradiated doped crystalline cytosine.H2O.

Following exposure to X-irradiation at low temperatures, the main reactions taking place in single crystals of cytosine monohydrate doped with minute amounts of 2-thiocytosine are hole transfer (HT) from the electron-loss centers to the dopant and recombination of oxidation and reduction products, assumedly by electron transfer. A huge deuterium kinetic isotope effect (KIE; >102-103) at 100 K, together with the kinetic curves obtained and density functional theory (DFT) calculations of equilibrium energy changes, indicates that these reactions proceed through a concerted proton-coupled electron/hole transfer where the proton transfer occurs between hydrogen-bonded cytosine molecules. The temperature dependence of these reaction rates between 10 and 150 K in normal and partially deuterated samples was investigated by monitoring the growth and decay of the various radical species over time using electron paramagnetic resonance (EPR) spectroscopy.

EPR and ENDOR study of crystalline cytosine x HCl doped with 5-methylcytosine. Radiation-induced radical formation and hole transfer.

Radical formation and hole transfer were investigated in crystals of cytosine.HCl (C.HCl) doped with 0-1.