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1980 (1)
1975 (1)
1Author    Hermann Esterbauer, Helmward Zöllner, N. Orbert ScholzRequires cookie*
 Title    Reaction of Glutathione with Conjugated Carbonyls  
 Abstract    1. GSH reacts with conjugated carbonyls according to the equation: G S H + R —C H = C H — COR R —CH(SG) —CH2—COR. The forward reaction follows second order, the reverse reaction first order kinetics. It is assumed that this reaction reflects best the ability of conjugated carbonyls to inactivate SH groups in biological systems. 2. The rate of forward reaction increases with pH approx. parallel with asH • Besides OH" ions also proton donors (e. g. buffers) increase the rate. The catalytic effect of pH and buffer is inter­ preted in view of the reaction mechanism. 3. The equilibrium constants as well as the rate constants for forward (k t) and reverse reaction show an extreme variation depending on the carbonyl structure. Acrolein and methyl vinyl ketone (k t = 120 and 32 mol-1 sec-1 , resp.) react more rapidly than any other carbonyl to give very stable adducts (half-lives for reverse reaction 4.6 and 60.7 days, resp.). Somewhat less reactive are 4-hydroxy-2-alkenals and 4-ketopentenoic acid (k t between 1 and 3 mol-1 sec-1), but they also form very stable adducts showing half-lives between 3.4 and 19 days. All other carbonyl studied react either very slowly (e. g. citral, ethly crotonate, mesityl oxide, acrylic acid) or form very labile adducts (crotonal, pentenal, hexenal, 3-methyl-butenone). Comparing biological activities of con­ jugated carbonyls their reactivity towards HS (/cj) and the stability of the adducts must be con­ sidered. 
  Reference    (Z. Naturforsch. 30c, 466—473 [1975]; received January 17/April 11975) 
  Published    1975 
  Keywords    Glutathione, Conjugated Carbonyls, Rate Constant, Equilibrium Constant 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0466.pdf 
 Identifier    ZNC-1975-30c-0466 
 Volume    30 
2Author    KlausJ N Eurohr, HenryH. MantschRequires cookie*
 Title    Complex Formation of Carnosine with Purine Nucleotides in Aqueous Solution  
 Abstract    This ^ -N M R study provides experimental evidence for an intermolecular interaction between the dipeptide carnosine (yS-alanyl-L-histidine) and the purine nucleoside 5'-m onophosphates 5'-AM P, 5'-IMP and 5'-GM P. From the observed upfield shifts o f the purine nucleotide and im idazole proton resonances it is concluded that the interaction is o f the stacking type and that it involves the purine base o f the nucleotide and the histidine m oiety o f carnosine. Apparent microscopic equilibrium constants and com plex shifts are obtained with a m icroscopic m odel, which considers the formation o f both 1:1 and 1 :2 complexes. The stacking pattern for com plex formation between the histidine m oiety o f carnosine and the adenine m oiety o f 5'-AM P is con­ structed by fitting the experimental 5'-AM P com plex for histidine. 
  Reference    Z. Naturforsch. 35c, 557 (1980); received D ecem ber 10 1979 
  Published    1980 
  Keywords    Carnosine, Purine N ucleotides, Proton N M R, Base Stacking, Equilibrium Constants 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0557.pdf 
 Identifier    ZNC-1980-35c-0557 
 Volume    35