The present paper deals with the nature and reactivity of paramagnetic species created during γ irradiation of sodium heparinate. Evidence for the presence of the <tex-math>$\dot{{\rm S}}{\rm O}{}_{3}{}^{-}$</tex-math> radical ion is given. The change in paramagnetism when irradiated samples are kept either under vacuum or in the presence of air has been studied; in both cases, the overall decrease seems to obey a first order kinetic law. We also have studied the reactivity of these paramagnetic species towards vinyl monomer vapors, so as to test the ability of heparin to be radiation grafted. Among the monomers tried, acrylic acid is the most efficient in decreasing the paramagnetism of irradiated samples and it is demonstrated that the <tex-math>$\dot{{\rm S}}{\rm O}{}_{3}{}^{-}$</tex-math> radical ion is not responsible for this phenomenon.

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