No abstract available

[en] Irradiated D-fructose solution exhibited marked enhancement in browning reaction with amino acid, and this effect depended on some radiolytic products of fructose. The radiolytic products formed in solution under aerated and anaerobic conditions were fractionated by column chromatography on Sephadex G-10, LH-20 and ion-exchange resin and by TLC on silica gel. The browning activity of each fraction was determined by reaction with glycine. The browning active products in the fraction were identified by GLC, GC-MS and TLC; they were: 6-deoxy-D-threo-2,5-hexodiulose, D-threo-2,5-hexodiulose, D-arabino-hexosulose and 4-deoxy-L-glycero-2,5-hexodiulose from irradiated solution under anaerobic conditions and D-threo-2,5-hexodiulose and D-arabinohexosulose from solution under aerated conditions. The browning reactions of the model compounds with glycine also indicated that D-threo-2,5-hexodiulose and 6-deoxy-D-threo-2,5-hexodiulose were more active than D-arabinohexosulose and 3-deoxy-D-erythrohexosulose. (author)

[en] Gamma-radiolosis of D-glucose in aqueous solution under anaerobic condition was investigated. D-glucose was significantly decomposed by action of a hydroxyl radical, a primary radiolytic product of water. Under anaerobic condition, glucose radicals formed by hydrogen abstraction of hydroxyl radical were dehydrated to give deoxygenated sugars, and a part of the radicals followed disproportionation reaction to afford dicarbonyl sugars. Among the products formed through these reactions, 2-deoxy-D-arabinohexono-1, 4-lactone (G in N₂=0.6, G in N₂O=0.8), 3-deoxy-D-erythrohexosulose and other 3-deoxy sugars as deoxygenated compounds, and D-arabinohexosulose and D-xylohexos-5-ulose as dicarbonyl compounds were identified. From these results, the radiolytic scheme of D-glucose in the absence of oxygen was proposed. (auth.)

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No abstract available

[en] Gamma-radiolysis of fructose in aqueous solution under aerated conditions formed various oxidized products, such as dicarbonyl hexoses, lower molecular aldoses and aldonic acids. Among these radiolytic products, D-arabinohexosulose (1, G = 2.2) and D-threo-2,5-hexodiulose (2, G = 1.5) were identified as major hexose derivatives, and D-threo-2,3-hexodiulose (3) and D-lyxo-hexos-5-ulose (4) as minor products. The radiolytic processes were found to be derived through fructose radicals, similarly to anaerobic radiolysis of fructose. The mechanism of radiolysis was proposed to be initiated by hydrogen abstraction with hydroxyl radical, followed by formation and degradation of fructose hydroperoxy radicals. (author)

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[en] Collagen was exposed to an ultraviolet (UV) lamp that emitted predominantly in the UVB range. The cross-linking of collagen type I and type IV by UV irradiation was observed. Amino acid analyses revealed that Tyr residues in both collagen types I and IV were decreased by irradiation. In collagen type IV, losses of His and Met residues were also observed. These losses of collagen type IV may be due to the degradation of Trp, which exists in collagen type IV and decreased drastically during UV irradiation. To clarify the mechanism of Tyr modification in both types of collagen, the degradation products of Tyr were analyzed. Dityrosine, which is a dimer of the Tyr residue, could not be detected in the acid hydrolysates of Uv-irradiated collagen. However, 3,4-dihydroxyphenylalanine, DOPA, was detected in the hydrolysates using HPLC with an electrochemical detector. The amounts of DOPA in the acid hydrolysates of collagen exposed to UV light for 24 h were approximately 350 pmol/mg protein (collagen type IV) and 80 pmol/mg protein (collagen type I). The DOPA formed may partially contribute to photoaging of the skin. (author)

No abstract available

No abstract available