Go toArchive
Browse byFacets
Bookbag ( 0 )
'Radical Reactions' in keywords
Results  10 Items
Sorted by   
Section
Publication Year
1983 (2)
1981 (1)
1978 (1)
1977 (3)
1976 (2)
1975 (1)
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 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0857.pdf 
 Identifier    ZNB-1976-31b-0857 
 Volume    31 
2Author    Requires cookie*
 Title    Radiation Chemistry of Carbohydrates, X* y-Radiolysis of Crystalline D-Glucose and D-Fructose  
 Abstract    i z d a r o g l u , D. H e n n e b e r g , K . N e u w a l d , G. S c h o m b u r g and C. v o n S o n n t a g In stitu t für Strahlenchemie im M ax-Planck-Institut für Kohlenforschung, Mülheim a. d. Ruhr a-D-Glucose and ß-D-fructose were y-irratiated in the solid (polycrystalline) state at room temperature at doses o f 3.5 • 1020-4 .2 • 1021 eV g-1 (dose rate 1.16 • 1018 eV g_1 min_1). Carbohydrate products containing < 6 carbon atoms were identified and their G-values (in parentheses) measured. Glucose: Dihydroxyacetone (1) (0.05), 3-deoxy-tetrose (2) (O.OI5), l,4-dideoxy-2-pentu-lose (3) (0.05), 2,4-dideoxy-pentose (4) (O.O8 5), 2,4-dideoxy-pentonic acid (5), 2,3-dideoxy-pentos-4-ulose (6) (together 0.03a), threose (7), erythrulose (8), erythrose (9), erythronic acid (10) (together 0.04), l-deoxy-2-pentulose (11) (0.005), 2-deoxy-ribose (12) (0.25), 3-deoxy-pentosulose (13) (0.02), 3,5-dideoxy-hexonic acid (14) (0.02), 2,3-dideoxy-hexonic acid (15) (0.01), arabinose (16) (0.25), ribose (17), ribonic acid (18) (together 0.02), 2-deoxy-2-C-hydroxymethyl-pentonic acid (19) (0.06), 5-deoxy-gluconic acid (20), 2-deoxy-5-keto-glucose (21), 2-deoxy-gluconic acid (22), 2-deoxy-3-keto-glucose (23), 3-deoxy-glucosone (24), 3-deoxy-gluconic acid (25), 3-deoxy-4-keto-glucose (26), 3-deoxy-mannonic acid (27) (together 0.4). Identified but nor measured quantitatively were glucosone (28), 3-keto-glucose (29), 4-keto-glucose (30), 5-keto-glucose (31) and gluconic acid (32). G(H2) = 5.75; G (C02) = 0.7. Fructose: 7-9 (together 0.65), 3-deoxy-pentonic acids (37), 3-deoxy-pentosulose (38) (together 0.3), arabonic acid (39) (0.1), 18 (0.05), 6-deoxy-2,5-hexodiulose (40) (40). Identified but not measured quantitatively were glyceraldehyde (34), butanone-(3)-diol-(l,2) (35) and 2 -and 3-deoxy-hexodiuloses. G(H2) = 4.75, G (C02) = 0.05. Reaction schemes are proposed to account for the form ation of the products. The scission of the hemiacetal bond and of the C-H and C-C bonds next to it appears to be typical for solid state irradiations. The formation of deoxy-compounds is observed both in the solid state and in aqueous solution. The form ation o f dideoxy-compounds is only prominent in the solid state. In polycrystalline fructose a chain reaction is induced leading to 6-deoxy-2,5-hexodiulose (40). 
  Reference    (Z. Naturforsch. 32b, 213—224 [1977]; received October 27 1976) 
  Published    1977 
  Keywords    GC-MS, G-Values, Radical Reactions, Chain Reaction 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-0213.pdf 
 Identifier    ZNB-1977-32b-0213 
 Volume    32 
3Author    Requires cookie*
 Title    Radiation Chemistry of Carbohydrates, XV OH Radical Induced Scission of the Glycosidic Bond in Disaccharides  
 Abstract    H e n r y k Z e g o t a * * a n d C l e m e n s v o n S o n n t a g In the y-radiolysis of deoxygenated, NaO-saturated aqueous solutions of maltose, lactose, gentiobiose, melibiose, trehalose and sucrose carbohydrate products containing five or six carbon atoms have been identified and their G-values measured. These products originate from the OH radical induced scission of the glycosidic bond of the disaccharides. The nature of the products is in agreement with a reaction scheme proposed previously for the radical induced scission of the glycosidic bond of cellobiose. It involves hydrolysis and the rearrangements of radicals with the free spin next to the glycosidic bond and to the lactol bridge. The nature the glycosidic bond (a, ß, 1-4, 1-6, 1-1, 1, 2) has only little influence on the G-values of its scission which range between about 1.9 and 3.5. 
  Reference    (Z. Naturforsch. 32b, 1060—1067 [1977]; received May 31 1977) 
  Published    1977 
  Keywords    y-Radiolysis, G-values, Mass Spectra, Radical Reactions 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-1060.pdf 
 Identifier    ZNB-1977-32b-1060 
 Volume    32 
4Author    Requires cookie*
 Title    Radiation Chemistry of DNA-Model Compounds, VII* On the Formation of 5-Deoxy-D-erythro-pentos- 4-ulose and the Identification of Twelve Further Products from y-Irradiated Aqueous Solutions of Ribose-5-phosphate  
 Abstract    L o t h a k S t e l t e r , C l e m e n s v o n S o n n t a g , a n d D i e t r i c h S c h u l t e -F r o h l i n d e Different mechanisms are considered to explain the formation of 5-deoxy-D-erythro-pentos-4-ulose in the y-radiolysis of ribose-5-phosphate in aqueous solution. On the basis of deuterium labelling experiments one mech­ anism involving an enol as an intermediate could be excluded. The identification of twelve further radio-lysis products from ribose-5-phosphate is reported. 
  Reference    (Z. Naturforsch. 30b, 656—657 [1975]; received February 19 1975) 
  Published    1975 
  Keywords    y-Radiolysis, Ribose-5-phosphate, Carbohydrates, Radical Reactions, Radical Cations 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0656_n.pdf 
 Identifier    ZNB-1975-30b-0656_n 
 Volume    30 
5Author    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 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0227.pdf 
 Identifier    ZNB-1976-31b-0227 
 Volume    31 
6Author    Requires cookie*
 Title    Photolysis (A = 185 nm) of Liquid Acetaldehyde Dimethyl Acetal  
 Abstract    H e in z -P e t e r S c h u c h m a n n a n d C l e m e n s v o n S o n n t a g In stitut fü r Strahlenchemie im M ax-Planck-Institut für Kohlenforschung, Mülheim a. d. R uhr Deaerated liquid acetaldehyde dimethyl acetal has been photolyzed at X = 185 nm, and 28 products have been determined. The m ajor ones with their quantum yields are: methanol (0.59), methane (0.26), ethyl methyl ether (0.17), m ethyl vin yl ether (0.16), m ethyl form ate (0.14), ketene dimethyl acetal (0.1), ethane (0.06), hydrogen (0.06), and acetaldehyde (0.06). The m ajor prim ary processes are suggested to be the scission o f the C-OCH3 bonds (homolytic and molecular) and o f the O-CH3 bonds (homolytic). Minor processes are hydrogen elimination reactions and the scission o f the C-CH3 bond. 
  Reference    (Z. Naturforsch. 32b, 205 [1977]; received October 8 1976) 
  Published    1977 
  Keywords    UV, GC-MS, Quantum yields, Radical Reactions, Fragm entation Processes 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-0205.pdf 
 Identifier    ZNB-1977-32b-0205 
 Volume    32 
7Author    Mohamed Al-Sheikhly, Clemens Von SonntagRequires cookie*
 Title      
 Abstract    The y-radiolysis of N20-saturated aqueous solutions generates OH radicals and a small amount of H atoms. In 1,3-dimethyluracil solutions (10 -3 M) these radicals add mainly to the 5-position of the C(5) -C(6) double bond of the solute. The resulting products have been identified by GC-MS after trimethylsilylation. The major products (G values in brackets) are dimers of the C(5)-OH-adduct radicals (3.4), 5,6-dihydro-5,6-dihydroxy-1,3-dimethyl-uracil (0.85), 5,6-dihydro-5-hydroxy-1,3-dimethyluracil (0.75), dimer of the C(5)-0H-adduct with the C(5)-H-adduct radical (0.2) and 5,6-dihydro-6-hydroxy-l,3-dimethyl-uracil (0.2). G(1,3-dimethyluracil consumption) has been found to be 5.7. The major reaction in this system is the dimerisation of the primary radicals. To a small extent the primary radicals also disproportionate by electron transfer to give the glycol 5,6-dihydro-5,6-dihydroxy-l,3-dimethyluracil as one of the products. Radiolytically formed H202 which could oxidise the C(5)-0H-adduct radical does not contribute to the formation of the glycol because the H202 yield is not reduced with respect to its expected "molecular yield" (G = 0.75). In contrast to the uracil system where it has been reported that drastic changes in radiolytic yields occur on going from neutral to alkaline irradiation conditions no such changes have been observed with 1,3-dimethyluracil. However, an acid-catalysed rearrangement from the C(5)-OH-adduct to the C(6)-0H-adduct radical is observed in the present system. 
  Reference    Z. Naturforsch. 38b, 1622—1629 (1983); received June 27 1983 
  Published    1983 
  Keywords    Hydroxyl Radicals, Electron Transfer Reactions, Radical Reactions, DNA Model Systems 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1622.pdf 
 Identifier    ZNB-1983-38b-1622 
 Volume    38 
8Author    J. Cadet, L. Voituriez, M. Berger, L. S. MyersRequires cookie*
 Title    Radiation-Induced Degradation of Purine and Pyrimidine 2'-Deoxyribonucleosides in Aqueous KBr Solutions  
 Abstract    Steady-state y-radiolysis of 5 x 10 -4 M pyrimidine and purine 2'-deoxyribonucleosides in aqueous solutions saturated with N2, N2O and O2, respectively, have been carried out in the presence of 0.1 M KBr. The main final degradation products have been isolated and characterised by various spectroscopic measurements including !H and 13 C NMR, UV, C.D. and mass spectrometry. The radiation-induced decomposition of thymidine is mostly accounted for by an ionic mechanism involving Br2, the decay product of Br2 --, as the reactive oxidising specie. On the other hand the degradation of the purine ring of 2'-deoxy-adenosine and 2'-deoxyguanosine may be accounted for by the action of Br2 --or Br3-2_ . 
  Reference    Z. Naturforsch. 38b, 1643—1651 (1983); received August 4/July 28 1983 
  Published    1983 
  Keywords    2'-Deoxyribonucleosides, Inorganic Radical, y-Irradiation, Radical Reactions, Thymidine Oxidation 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1643.pdf 
 Identifier    ZNB-1983-38b-1643 
 Volume    38 
9Author    BarryJ. Parsons, Dietrich Schulte-Frohlinde, Clemens Von SonntagRequires cookie*
 Title    Reaction of Br3' 2 -with 2-Deoxy-D-ribose. A Preferred Attack at C-l  
 Abstract    In the photolysis of 5-bromouracil containing DNA Br atoms are expected inter mediates. In order to evaluate the possible site of attack of the Br atom at the sugar moiety of DNA the reaction of 2-deoxy-D-ribose with the Br atom (complexed with two bromide ions) was investigated. Hydroxyl radicals generated by the radiolysis of N20 saturated aqueous solutions were converted into Br3 -2_ radicals by 1 M bromide ions. Br3-2-reacts with 2-deoxy-D-ribose (k = 3.7 • 10 4 M -1 s -1 , pulse radiolysis). The major product is 2-deoxy-D-erythro-pentonic acid (G = 2.4, y-radiolysis). It is formed by hydrogen abstraction from C-l and oxidation of this radical by other radicals. An alternative route via the radical at C-2 is neglible. It follows that Br3-2 ~ reacts preferentially at C-l of 2-deoxy-£>-ribose. 
  Reference    Z. Naturforsch. 33b, 666—668 (1978); received March 15 1978 
  Published    1978 
  Keywords    Pulse Radiolysis, y-Radiolysis, 2-Deoxy-D-ribose, G-values, Radical Reactions 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0666.pdf 
 Identifier    ZNB-1978-33b-0666 
 Volume    33 
10Author    Henryk Zegota++, Clemens Von SonntagRequires cookie*
 Title    Radical-Induced Dephosphorylation of Fructose Phosphates in Aqueous Solution +  
 Abstract    Oxygen free N20-saturated aqueous solutions of D-fructose-1-phosphate and D-fructose-6-phosphate were y-irradiated. Inorganic phosphate and phosphate free sugars (containing four to six carbon atoms) were identified and their G-values measured. D-Fructose-1-phosphate yields (G-values in parentheses) inorganic phosphate (1.6), hexos-2-ulose (0.12), 6-deoxy-2,5-hexodiulose (0.16), tetrulose (0.05) and 3-deoxytetrulose (0.15). D-Fructose-6-phosphate yields inorganic phosphate (1.7), hexos-5-ulose (0.1), 6-deoxy-2,5-hexodiulose (0.36), 3-deoxy-2,5-hexodiulose and 2-deoxyhexos-5-ulose (together 0.18). On treatment with alkaline phosphatase further deoxy sugars were re-cognized and in fructose-1-phosphate G(6-deoxy-2,5-hexodiulose) was increased to a G-value of 0.4. Dephosphorylation is considered to occur mainly after OH attack at C-5 and C-l in fructose-1-phosphate and at C-5 and C-6 in fructose-6-phosphate. Reaction mechanisms are discussed. 
  Reference    Z. Naturforsch. 36b, 1331—1337 (1981); received May 29 1981 
  Published    1981 
  Keywords    D-Fructo8e-l-phosphate, D-Fructose-6-phosphate, y-Irradiation, Radical Reactions, Mass Spectrometry 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-1331.pdf 
 Identifier    ZNB-1981-36b-1331 
 Volume    36