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'Radical Reactions' in keywords Facet   Publication Year 1976  [X]
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1Author    ClemensVon Sonntag, Miral Dizdaroglu, Dietrich Schulte-FrohlindeRequires cookie*
 Title    y-Radiolysis of Cellobiose in N20-saturated Aqueous Solution Part II. Quantitative Measurements. Mechanisms of the Radical-induced Scission of the Glycosidic Linkage  
 Abstract    The y-radiolysis of cellobiose (10 -2 M) in N2O saturated aqueous solution has been investigated and the G-values of the following 21 products containing six or less C-atoms have been measured (G-values in parentheses): glucose (2.1), gluconic acid (0.70), 4-keto-glucose (0.07), 5-keto-glucose (0.05), 4-deoxy-glucose (0.27), 5-deoxy-gluconic acid (0.18), 2-deoxy-gluconic acid (0.13), 3-deoxy-4-keto-glucose (0.23), 2-deoxy-5-keto-glucose (0.34), 4-deoxy-5-keto-glucose (0.14), 6-deoxy-5-keto-glucose (0.02), arabinose (0.07), ribose (0.015), 2-deoxy-ribose (0.17), 3-deoxy-pentulose (0.01), erythrose (0.015), threose (0.015), 2-deoxy-tetrose (0.01), butanone-(2)-diol(1.4) (0.01), dihydroxyacetone (0.01), carbon monoxide (> 0.02). The formation of the major part (98%) of the measured products could be explained on the base of the following assumption: The first step of reaction sequence is abstraction of H atoms from C-H bonds of the cellobiose by OH radicals. Radicals at C-l', C-5' and C-4 and their successors undergo in a second step four types of reactions: hydrolysis, re-arrangement and H2O and CO elimination. In a third step the transformed radicals give rise to products by disproportionation reaction. Only two products out of 16 predicted under the above assumption are not observed. G-values for the attack at C-l', C-5' and C-4 are 1.4, 0.6 and 0.3 respectively. 
  Reference    (Z. Naturforsch. 31b, 857—864 [1976]; received February 25 1976) 
  Published    1976 
  Keywords    Carbohydrates, Radical Reactions, y-Radiolysis, Cellobiose, Glycosidic Linkage 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0857.pdf 
 Identifier    ZNB-1976-31b-0857 
 Volume    31 
2Author    Mibal Dizdaroglu, Klaus Neuwald, ClemensVon SonntagRequires cookie*
 Title    Radiation Chemistry of DNA Model Compounds, IX* Carbohydrate Products in the y-Radiolysis of Thymidine in Aqueous Solution. The Radical-Induced Scission of the N-Glycosidic Bond  
 Abstract    In the y-radiolysis of deoxygenated N20-saturated aqueous solutions of thymidine (10-3 M, room temperature, dose rate 4 • 10 18 eV/g.h., dose 6.7 10 17 -3.3 • 10 18 eV/g) the following products (G-values in parentheses) have been identified: 2,5-dideoxy-pentos-4-ulose (1) (0.01), 2,4-dideoxy-pentodialdose (2) (0.02), 2,4-dideoxy-pentos-3-ulose (3) (0.03), 2,3-dideoxy-pentos-4-ulose (4) (0.01), 2-deoxy-pentos-4-ulose (5) (0.1), 2-deoxy-ribonic acid (6) (0.02) and thymine (8) (< 0.2). In the presence of oxygen (N20/02 80/20 v/v saturated) products 1-4 are absent, G (5) = 0.2, G (6) = 0.07 and G (8) < 0.4. Further-more, 2-deoxy-tetrodialdose (7) which is absent in deoxygenated solution is formed with a G-value of 0.03. Mechanisms are proposed to account for the scission of the N-glycosidic linkage. Product 6 is thought to be due to a primary OH radical attack at C-l' of the sugar moiety, 3 arises from an attack at C-3', 1, 4 and 5 from an attack at C-4', and 2 and 7 from an attack at C-5'. 
  Reference    (Z. Naturforsch. 31b, 227—233 [1976]; received September 24 1975) 
  Published    1976 
  Keywords    Thymidine, Radiolysis, Radical Reactions, GC-MS, DNA Model Compounds 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0227.pdf 
 Identifier    ZNB-1976-31b-0227 
 Volume    31