ESR and ENDOR study of adenosine single crystals X-irradiated at 10 K.
Single crystals of adenosine were X-irradiated at 10 K and investigated between 10 and 300 K using K-band ESR and ENDOR spectroscopy. Two free radicals were analyzed. Radical I exhibits small hyperfine couplings to the C8-H, C2-H, and a N3-H protons, and was identified as the N3 protonated base anion radical. Radical II exhibits small hyperfine couplings to a C8-H and an exocyclic -N10-H proton. It is suggested that this is therefore the N10 deprotonated base cation radical. Enough data were not available to analyze a third primary radical believed to be located on the ribose moiety. Upon warming Radical I decays at ca. 40 K with no apparent successor. Likewise, no successor was identified for Radical II, which decays at ca. 100 K. At ca. 200 K there is ESR evidence for the C2 and C8 H-addition radicals. Their precursors have not been identified.
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Department of Physics, East Tennessee State University, Johnson City 37614.
Nelson
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D000241:Adenosine / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005615:Freezing; D009686:Nuclear Physics
D005609:Free Radicals; D000241:Adenosine