title: Electron paramagnetic resonance of X-irradiated sodium and potassium salts of glucose-1-phosphate. Identification of PO3(2-) radicals at room temperature.
abstract: Single crystals of the disodium and dipotassium salt of glucose-1-phosphate, X-irradiated at 80 K or at 280 K, show the presence of PO3(2-) radicals at 295 K, formed by scission of the phosphate-ester bond at the phosphate side. The 31P hyperfine coupling constants were measured using X- and Q-band EPR spectroscopy. Typical values for these coupling constants are a magnitude of = 68 mT and a perpendicular = 53 mT. The g values were almost isotropic, slightly smaller than that of the free electron spin (g = 2.0023). There is no substantial reorientation of the phosphate group in the crystalline lattice upon radical formation. Directly after irradiation at 77 K the PO3(2-) radicals are not present, but their characteristic resonance grows in upon thermal annealing of the crystals. The radicals are probably formed from a carbon-centered radical precursor by secondary reactions resulting in the loss of the phosphate group, leaving a (diamagnetic) modified carbohydrate molecule behind. The alternative process of reductive cleavage of the phosphate-ester bond by electrons released from traps in the crystal upon thermal annealing is considered less likely. A second phosphate-centered species, with a magnitude of about 21 mT and a perpendicular about 15 mT, was detected in the dipotassium salt of glucose-1-phosphate only. Possible structures for this species are discussed.
authors.affiliation: Department of Physics, University of Oslo, Norway.
authors.forename: B
authors.initials: B
authors.lastname: Bungum
authors.forename: E O
authors.initials: EO
authors.lastname: Hole
authors.forename: E
authors.initials: E
authors.lastname: Sagstuen
authors.forename: M
authors.initials: M
authors.lastname: Lindgren
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005958:Glucosephosphates / Q000737:chemistry* / Q000528:radiation effects*; D013696:Temperature
chemical_list: D005609:Free Radicals; D005958:Glucosephosphates; C031590:glucose-1-phosphate