title: Analysis of paramagnetic centers in X-ray-irradiated enamel, bone, and carbonate-containing hydroxyapatite by electron spin resonance spectroscopy.
abstract: Carbonate-containing hydroxyapatite, enamel, and bone were irradiated by an X-ray and investigated between 77 degrees and 350 degrees K by means of electron spin resonance (ESR) spectroscopy. The ESR spectrum of enamel irradiated at 77 degrees K in vacuum and observed at the same temperature was almost the same as that of the carbonate-containing hydroxyapatite. The temperature dependence of signal intensities confirms a spin-energy exchange between the mineral and organic constituents in bone, but in enamel no or very little spin-energy exchange between the mineral and organic constituents. Considerable similarity among the ESR spectra of enamel, bone, and carbonate-containing apatite was obtained after X-ray irradiation in air at 300 degrees K with both an X-band and a Q-band ESR spectrometer. The Q-band spectrum can be interpreted in terms of two paramagnetic species. One is identified as a CO3(3-) anion radical which has an axial symmetry with g factors of 2.0029 and 1.9972. The other species is found to be centered at g = 2.0019.
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000528:radiation effects*; D002254:Carbonates / Q000528:radiation effects*; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003743:Dental Enamel / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy; D006358:Hot Temperature; D006882:Hydroxyapatites / Q000528:radiation effects*; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature; D014965:X-Rays
chemical_list: D002254:Carbonates; D006882:Hydroxyapatites