Kunihiko Nakata

X-ray study of beijeran sodium salts, a new galacturonic acid-containing exo-polysaccharide.

X-Ray fiber diffraction patterns were obtained from oriented films of sodium salts of a new uronic acid-containing polysaccharide (beijeran) both in its native, poly [-->3)-alpha-D-GalA-(1-->3)-beta-L-Rha-(1-->3)-alpha-D-Glc-O6Ac-(1 -->], and deacetylated forms. Initially the stretched films of both polysaccharides were amorphous, but the crystallinity was much improved by annealing at high temperature. The deacetylated specimen had higher crystallinity than the native. Both films showed similar X-ray fiber patterns indicating that these polysaccharides had similar unit cell dimensions and that the O-acetyl groups in the native beijeran chain did not disturb the regular array in the crystal having space group P21. All the visible reflections could be indexed in terms of a monoclinic unit cell with dimensions a = 1.277, b = 1.611, c (fiber axis) = 2.437 nm, and gamma = 96.79 degrees. The fiber axis length and the presence of (002) and (006) reflections indicated that the conformation was made up of two trisaccharide residues, in an extended two-fold helix.

Oxidation intermediates of l-ascorbic acid 2-glucoside by pulse radiolysis

Abstract Radical species generated from l -ascorbic acid 2-glucoside (2-G-AH) and OH radicals (OH • ) or azide radicals (N 3 • ) were investigated by pulse radiolysis. The OH adduct radicals formed by the reaction of 2-G-AH with OH • were converted into the ascorbic acid radical (A •− ) in alkaline solutions with the elimination of glucose. Oxidation radicals with a broad absorption spectrum were produced directly upon oxidation of 2-G-AH by the oxidizing N 3 • , and some of these radicals were converted into A •− in strongly alkaline solutions. Ascorbic acid was detected from 60 Co γ ray irradiation on strongly alkaline N 2 O-saturated solutions of 2-G-AH owing to disproportionation of the A •− .

Oxidation intermediates of α-glucosyl rutin by pulse radiolysis

Abstract Transient intermediates generated in the reaction of α-glucosyl rutin (G-rutin) with the OH radical or the azide radical were investigated by pulse radiolysis. The OH radical reacted with G-rutin to produce the OH-adduct radical, followed by deprotonation in neutral and acidic solutions. In alkaline solutions, the OH-adduct di-anion radical formed from the di-anions of G-rutin were dehydrated to the phenoxyl radical. On the other hand, G-rutin was oxidized to one-electron oxidized cation radical by the azide radical. The pK a values of the OH radical adduct were found to be 6.83 ± 0.10 and 8.87 ± 0.13. While, the pK a values of the phenoxyl radical of G-rutin were found to be 7.52 ± 0.11 and 9.95 ± 0.13.

Oxidized intermediates formed from α- and β-galactosyl ascorbic acid by pulse radiolysis

Abstract The formation of OH-adduct radicals and the one-electron oxidation radicals of 6-O-α- and β-galactosyl ascorbic acid (α- and β-GA) were studied by pulse radiolysis. The OH-adduct radicals formed by the reaction between α- or β-GA and OH radicals were converted to their dehydrated radicals in neutral and alkaline solutions. The rate constants for reactions between OH radicals and α- or βGA were slightly smaller than that of ascorbic acid (AsA). The rate constants for the formation of oxidized radicals of GA with N3 radicals were smaller than those of OH-adduct radicals. The rate constants for the decay of the α- or β-forms of galactosyl ascorbate radicals were twice as fast as that of AsA. The oxidized radicals of GA were found to decay by a disproportionation reaction on γ-ray irradiation.

Detection of oxidation radicals of 2,3-enediol form of 2,3-dioxoguluno-δ-lactone by pulse radiolysis

The OH adduct radicals of the 2,3-enediol form of 2,3-dioxoguluno-δ-lactone (2,3-End.DKGL) have been observed in aqueous solution by puise radiolysis (the adduct radicals were converted into the one-electron oxidation radical in alkaline solutions by dehydration); the oxidation radical has also been produced by oxidation of 2,3-End.DKGL by the azide radical (N3˙).