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1Author    Peter Laggner, Josef Suko, Christian Punzengruber, Rudolf PragerRequires cookie*
 Title    Electron Spin Resonance Studies on Conformational Changes of the Sarcoplasmic Reticulum Ca 2+ -ATPase Induced by Synergistic Action of Calcium and ATP  
 Abstract    Changes in motional properties of the -SH group environment in sarcoplasmic reticulum ATPase [1] induced by addition of specific ligands to sarcoplasmic reticulum membrane vesicles were investigated systematically by electron spin resonance (e.p.r.) spectro-scopy. Alternatively, two kinds of iodoacetamide analog spin labels, 4-(2-iodoacetamido)-2,2,5,5-tetramethyl-l-pyrrolidinyl-N-oxyl (label I) and 4-(2-iodoacetamido)-2,2,6,6-tetra-methyl-l-piperidinyl-N-oxyl (label II) were used. The labeling conditions were chosen such that less than three moles of -SH groups per mole of ATPase reacted with the spin labels. A marked increase in isotropic motion of either spin label was observed on addition of calcium in millimolar concentrations plus ATP or /S-y-methylene ATP. Qualitatively similar but smaller changes were also observed with inosine 5'-triphosphate (ITP), acetylphosphate, or ADP in the presence of calcium. These effects were independent of added magnesium. The spectral changes induced by ß-y-methylene ATP, which binds to the ATPase but is not hydrolyzed, and those of calcium plus ADP suggest a conformational change due to simultaneous binding of these ligands in the absence of enzyme phosphoryla-tion. These changes in e.p.r. spectra were different in quality and magnitude from those observed upon separate binding of calcium or adenine nucleotides. The two spin labels, differing only in their numbers of heterocyclic ring atoms, were found to reflect environmental changes in different ways. This demonstrates the usefulness of employing different spin labels to detect and interpret structural transitions in macro-molecular assemblies. The active transport of calcium by sarcoplasmic reticulum membranes isolated from skeletal muscle is generally considered to be a multistep process [1, 2], Several models for the reaction sequence of calcium translocation by the calcium pump of sarcoplasmic reticulum have been proposed on the basis of kinetic experiments [2-11]. In order to detect and characterize structural alterations of the ATPase in the calcium transport cycle, e.p.r. spectroscopic investigations of spin-labeled sarco-plasmic reticulum preparations, first introduced by 
  Reference    Z. Naturforsch. 36b, 1136—1143 (1981); received February 2 1981 
  Published    1981 
  Keywords    Sarcoplasmic Reticulum, Spin Labeling, Calcium-ATPase 
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 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-1136.pdf 
 Identifier    ZNB-1981-36b-1136 
 Volume    36 
2Author    Martin Jäger1, Paul Schuler1, HartmutB. Stegmann, Antal RockenbauerbRequires cookie*
 Title    Molecular Recognition Analyzed by Observing Intramolecular Interconversion with E PR Spectroscopy  
 Abstract    Molecular recognition between Rebek's cleft R and 4-(2-benzimidazolyl)-aminomethyl-2,6-di-rm-butyl-phenol (Bi) is investigated by means of EPR spectroscopy. Their specific inter-molecular interactions are distinguished from non-specific interactions represented by mere protonation on addition of benzoic acid. Both interactions are related to intramolecular in­ terconversions at the CQ-atom of Bi*, where a two-jump mechanism is found for free and protonated Bi* and a two-site exchange for the complexed ligand. While NMR spectroscopy indicates the existence of 1:1 and 1:2 receptor-substrate complexes, the faster time scale of EPR spectroscopy allows to identify one 1 : 2 as well as three 1 : 1 associates and to elucidate their formation conditions. Based upon the corresponding hf parameters, binding modes and sites are proposed for the key-in-the-lock system. 
  Reference    Z. Naturforsch. 53b, 1511—1519 (1998); received July 22 1998 
  Published    1998 
  Keywords    Rock-Key-Equilibria, Spin Labeling, Molecular Dynamics 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-1511.pdf 
 Identifier    ZNB-1998-53b-1511 
 Volume    53 
3Author    G., R. Ia, N. IeRequires cookie*
 Title    Investigation of Inductive Effects on the Transphosphorylation Reaction of Spin-Labeled Phosphoryl Imidazolides, Part  
 Abstract    Spin-labeled phosphoryl imidazolides 3, 6 , and 7 were prepared and compared to the unsubstituted compound 1 in reactivity towards hydroxy and amino compounds. The transphorphorylation reaction of compounds 3 and 6 was slower than that of 1. The reaction of compound 6 was selective towards amines since no reaction occurred with hydroxy compounds. The reaction of compounds 7 was slow with hydroxy compounds and rapid with amines at room temperature. The transphorphorylation reaction of 1 was rapid with both hydroxy and amino compounds at 50-55 °C. 
  Reference    (Z. Naturforsch. 32b, 1182—1188 [1977]; received July 4 1977) 
  Published    1977 
  Keywords    Spin-Labeling, Nitroxyl, Imidazoles, Spin-Labeled Phosphates, Spin-Labeled Phosphoroamidates 
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 TEI-XML for    default:Reihe_B/32/ZNB-1977-32b-1182.pdf 
 Identifier    ZNB-1977-32b-1182 
 Volume    32 
4Author    Maria Konieczny, George SosnovskyRequires cookie*
 Title    Reaction of Trivalent Organophosphorus Compounds with Selenium  
 Abstract    Selenium derivatives of pentavalent organophosphorus compounds 9, 10, 11 (R = 2,2,6,6-tetramethyl-l-oxyl-4-piperidyl), 12 and 13 were prepared in 79-99% 
  Reference    Z. Naturforsch. 33b, 1040—1046 (1978); received June 2 1978 
  Published    1978 
  Keywords    Nitroxyl Radical, Selenium, Organoselenophosphorus Compounds, Phosphorus Compounds, Spin-labeling 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1040.pdf 
 Identifier    ZNB-1978-33b-1040 
 Volume    33 
5Author    S. Mazzuca, L. SportelliRequires cookie*
 Title    Thermal Behaviour of Lymphocyte Membrane: ESR Investigation  
 Abstract    The order parameter, S, of the plasma membrane of in toto human peripheral blood lym­ phocytes was obtained by electron spin resonance spectroscopy in the temperature range 25-41 C. This membrane is completely in the liquid crystalline state above 31 C. In presence of the antigen ETB from Staphylococcus aureus at the concentration of 4 (ig/3 * 107 cells an overall decrease of the order parameter for this membrane is observed. The decrease of 5 is followed by an upwards shift at about 35 C of the temperature of the liquid crystalline state. 
  Reference    Z. Naturforsch. 45c, 1060—1062 (1990); received April 6 1990 
  Published    1990 
  Keywords    Plasma Membrane, Lymphocyte, Phase Transition, Staphylococcal Enterotoxin B, Spin Labeling 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-1060.pdf 
 Identifier    ZNC-1990-45c-1060 
 Volume    45 
6Author    G. Eo Rg, S. Osnovsky, ShuW. En, Li, M. Ahesw, AraR. AoRequires cookie*
 Title    In the Search for New Anticancer Drugs, XXI. Spin Labeled Nitrosoureas  
 Abstract    The spin labeled nitrosoureas 7 a—e and 12 were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukem ia P388. C om pounds 7 a —c, 7 e and 12 possessed activities ranging from 31 to 542 percent increase in life span (% IL S), w hereas com ­ pound 7 d was marginal (% IL S = 21). All CD2Fj male mice treated with the most active com ­ pounds (7a and 12) at 35 mg/kg for 9 days were alive after 30 days, w hereas all mice treated with the clinical drug CCNU (lc) succumbed. Compounds 7 a —e and 12 were further evalu­ ated for their antineoplastic activity against lymphoid leukem ia L1210. C om pounds 7a and 12 exhibited, on day 60, a % ILS of 713 and 620, respectively. The lipophilicities of com pounds 7 a —e and 12 were determ ined using the E PR and UV methods. Compounds 7a and 12 which differ from CCNU and M eCCNU by the replacement of the cyclohexyl and methylcyclohexyl groups with six and five m em bered nitroxyl radical moieties were more hydrophilic than the clinical drugs. 
  Reference    Z. Naturforsch. 42c, 921—931 (1987); received August 14 1986 
  Published    1987 
  Keywords    Nitrosoureas, Nitroxyl Radicals, Spin Labeling, Anticancer Drugs, Leukemia P388 and L1210 
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 TEI-XML for    default:Reihe_C/42/ZNC-1987-42c-0921.pdf 
 Identifier    ZNC-1987-42c-0921 
 Volume    42