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1988 (1)
1984 (1)
1980 (1)
1Author    CherlaP. Murthy, DavidJ. Deeble, Clemens Von SonntagRequires cookie*
 Title    The Formation of Phosphate End Groups in the Radiolysis of Polynucleotides in Aqueous Solution  
 Abstract    The polynucleotides poly(U), poly(C), poly(A) and poly(G) have been y-irradiated in N20-and N20/02 (4:l)-saturated aqueous solutions. Hydroxyl radicals from the radiolysis of water react with the polynucleotides thereby producing among other lesions strand breaks. Strand break-age is connected with the formation of phosphomonoester end groups. Such end groups have been determined by measuring inorganic phosphate after a three hour incubation at 37 °C with acid or alkaline phosphatase. In the absence of oxygen G(phosphomonoester end groups) (in units of i^mol J' 1) are 0.47 (poly(U)), 0.17 (poly(C)) and < 0.04 (poly(A) and poly(G)). In the case of poly(U) and poly(C) on heating the sample for one hour at 95 °C prior to incubation with phosphatases the above values increased by 0.14 and 0.07 jxmol J" 1 , resp., whereas such treatment of the purine poly-nucleotides still did not produce a measurable yield of phosphomonoester end groups. Comparing these values with G values for strand breakage taken from the literature, about two phospho-monoester end groups are formed per strand break in poly(U) while for poly(C) this ratio is about unity. The purine polynucleotides show very low yields of strand breakage in agreement with the negligible phosphomonoester yields. In the presence of oxygen G(phosphomonoester end groups) are 0.46 (poly(U)), 0.21 (poly(C)), and < 0.04 (poly(A) and poly(G)). On heating, these values increase, most markedly for poly(U) and poly(C). This is possibly linked to the decomposition of unstable hydroperoxides which are formed in high yields in poly(U) and poly(C) (G = 0.7 and 0.19 nmol J resp.). It is known that at least in the case of poly(U), base radicals attack a sugar moiety and are the main precursors of these lesions. G(phosphomonoester end groups) are considerably lower in the case of the purine polynucleotides. Whether this is due to an inability of the base radicals to attack a sugar moiety or has other reasons must remain an open question. 
  Reference    Z. Naturforsch. 43c, 572—576 (1988); received March 14 1988 
  Published    1988 
  Keywords    Polynucleotides, Strand Break, Phosphomonoester End Group, Oxygen Effect 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0572.pdf 
 Identifier    ZNC-1988-43c-0572 
 Volume    43 
2Author    D. Schulte-Frohlinde, E. BotheRequires cookie*
 Title    Identification o f a M ajor Pathway of Strand Break Form ation in Poly U Induced by O H Radicals in Presence o f O xygen  
 Abstract    A reaction m echanism is presented for stra n d b re ak form ation in poly U induced by O H radicals in N 20 / 0 2-saturated aqueous solution based on experim ental results obtained with different m ethods. 
  Reference    Z. Naturforsch. 39c, 315—319 (1984); received D ecem ber 27 1983 
  Published    1984 
  Keywords    Strand Break Form ation, Poly U, Oxygen Effect, D N A 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0315_n.pdf 
 Identifier    ZNC-1984-39c-0315_n 
 Volume    39 
3Author    GünterF. Wildner, PrafullachandraV. Sane, Jürgen HenkelRequires cookie*
 Title    The Activation of Ribulose-l,5-bisphosphate Carboxylase-Oxygenase from Spinach by Oxygen Changes of the Enzyme Conformation during Air-Argon Transitions  
 Abstract    The effect of oxygen on ribulose-l,5-bisphosphate carboxylase-oxygenase from spinach was in­ vestigated. Both activities were deactivated by removal of oxygen and reversibly reactivated by oxygenation of the enzyme solution. The change in enzyme activities was accompanied by confor­ mational changes as studied by the use of intrinsic and extrinsic fluorescent probes. The analysis of cysteine sulfhydryl groups accessible to 5,5'-dithiobis-(2-nitrobenzoic acid) re­ vealed that the number of these groups changed with the oxygen concentration. The kinetic of the exposure of eight cysteine residues was similar to the loss of enzyme activities. The modification of these groups with 5,5'-dithiobis-(2-nitrobenzoic acid) caused almost complete loss of both the activities. The enzyme isolated from a photolithotrophic organism, Chromatium vinosum, was not affected by oxygen removal. During air — argon transitions, neither the enzyme conformation nor the num­ ber of accessible sulfhydryl groups changed. 
  Reference    Z. Naturforsch. 35c, 239—248 (1980); received December 12 1979 
  Published    1980 
  Keywords    Ribulose-l, 5-bisphosphate Carboxylase, Ribulose-l, 5-bisphosphate Oxygenase, Enzyme Confor­ mation, Oxygen Effect, Photosynthesis 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0239.pdf 
 Identifier    ZNC-1980-35c-0239 
 Volume    35