title: The mechanism of CO2- radical formation in biological and synthetic apatites.
abstract: Biological apatites (tooth enamel, bone) and their synthetic analogues were exposed to gamma rays, UV light, or thermal treatment and studied by electron paramagnetic resonance (EPR). The thermal generation of CO2- radicals in synthetic apatite was observed for the first time. It was shown that the experimental EPR spectra of all of the above-mentioned materials are caused by the contribution of two types of CO2- radicals: axial and orthorhombic. The ratio of their concentrations depends on the characteristic energy of the external influence (i.e., the energy of quantum for radiation or kT for thermal treatment) and also on the quality of the initial material (defectiveness). Based on the analysis of EPR spectra recorded immediately after gamma-irradiation, the authors conclude that the main short-lived radical in bioapatites is CO3(3)- . The unified mechanism of CO2- radical formation in hydroxyapatites at different external influences is proposed; the main stages of transformation are CO3(2)- + e --> CO3(3)- --> CO2-, where the electron (e) originates from the ionization of impurities by radiation/temperature.
authors.affiliation: Institute of Semiconductor Physics of NAS of Ukraine, 45, pr. Nauky, Kiev, 03028, Ukraine. vv_rudko@yahoo.com
authors.forename: V V
authors.initials: VV
authors.lastname: Rudko
authors.forename: I P
authors.initials: IP
authors.lastname: Vorona
authors.forename: N P
authors.initials: NP
authors.lastname: Baran
authors.forename: S S
authors.initials: SS
authors.lastname: Ishchenko
authors.forename: I V
authors.initials: IV
authors.lastname: Zatovsky
authors.forename: L S
authors.initials: LS
authors.lastname: Chumakova
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry / Q000528:radiation effects; D001842:Bone and Bones / Q000737:chemistry* / Q000528:radiation effects*; D002245:Carbon Dioxide / Q000737:chemistry* / Q000528:radiation effects; D002417:Cattle; D003743:Dental Enamel / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005609:Free Radicals / Q000737:chemistry; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry* / Q000528:radiation effects*; D011829:Radiation Dosage; D013552:Swine
chemical_list: D005609:Free Radicals; D006882:Hydroxyapatites; D002245:Carbon Dioxide