Paramagnetic molecular centers in gamma-irradiated aluminum hydroxide complexed with glycine or serine

Paramagnetic molecular centers produced by gamma irradiation at 77 K and at 293 K in Alx(OH)y, when precipitated with glycine or serine, were studied by ESR spectroscopy. Stable paramagnetic centers characteristic for the amino acid were observed only in the complexes with DL-alpha-serine, and only in air. In the absence of air, at 293 K, none of the paramagnetic centers gave ESR spectra characteristic of the amino acids examined. Irradiation at 77 K produced the glycine radical, .CH2COOH, only in the complex prepared at pH 6.8 and not in the complex prepared at pH 9.5. The radical decayed when the sample was warmed. In the serine complexes, at 77 K the radicals characteristic of the amino acid were not observed. Differences in the behavior between glycine and serine in the complexes prepared under similar conditions are probably due to the serine OH group available for hydrogen bonding in the matrix.