Isotropic radical CO 2 - in biological apatites

The isotropic CO 2 - EPR spectrum at g ∼ 2.0006 for γ -irradiated powders of dental enamel annealed at different temperatures up to 320 ∘ C is studied. The signal intensity is found to increase with the growth of annealing temperature up to 240 ∘ C . This finding contradicts to the existing model of isotropic CO 2 - radical in apatites. The possible models of the radical in biological apatite are analyzed and discussed. On the basis of the results obtained it is suggested that in tooth enamel apatite the isotropic CO 2 - radical is the bulk radical localized in structural voids of hydroxyapatite lattice, which occur in the vicinity of a carbon radical in position B.