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1981 (1)
1980 (1)
1Author    G. Ünther Bernhardt, Rainer Rudolph, Rainer JaenickeRequires cookie*
 Title    Reassociation of Lactic Dehydrogenase from Pig Heart Studied by Cross-Linking with Glutaraldehyde  
 Abstract    Cross-linking with glutaraldehyde has been successfully applied in order to analyze the kinetics of reassociation of oligomeric enzymes (R. Hermann, R. Rudolph, and R. Jaenicke Nature 277, 243-245 (1979)). In the present study the assembly of lactic dehydrogenase from pig heart is investigated using this approach. In order to eliminate perturbations caused by excessive folding reactions, acid dissociation was performed in the presence of 0.8 M Na2S 0 4 at 0°C . Under optimum conditions complete cross-linking of the tetrameric enzyme was achieved in less than 2 minutes. Cross-linking during reconstitution proves the dimer to be the only intermediate of reasso­ ciation. The dimer -*■ tetramer transition is found to be rate-limiting for both reassociation and reactivation, suggesting the tetramer to be the enzymatically active species. The presence of monomers during reconstitution indicates that tetramer formation is preceded by a fast monomer-dimer equilibrium. The kinetic model describing the experimental data 4M^2D^T is characterized by an equilibrium constant K = 3 ± 1 • 107 liter • m ol-1, and a second-order rate constant k = 1.4 ± 0.2 • 104 liter • mol-1 • s-1. 
  Reference    Z. Naturforsch. 36c, 772—777 (1981); received May 15 1981 
  Published    1981 
  Keywords    Cross-Linking, Glutaraldehyde, Lactic Dehydrogenase, Reassociation, Reconstitution 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0772.pdf 
 Identifier    ZNC-1981-36c-0772 
 Volume    36 
2Author    Alexandru Popescu, Stefan Antohi, Stefan Trasculescu, Adriana Aurescu, NicolaeM. Anolescu, Victor CiocnituRequires cookie*
 Title    Changes Induced by Pre-Fixation in Polycation Bacteriolysis and Surface Alterations Matching the Model of Wall Picnosis in Cell Lysis  
 Abstract    Pretreatments of B. subtilis and S. aureus cells with lower concentrations of fixative agents, led to modifications in bacteriolytic effect exerted by polyarginine and protamine: Glutaraldehyde blocked polycation bacteriolysis while formaldehyde and osmium tetroxide (0 s0 4) having no influence on polyarginine action, increased constantly the cell sensitivity to protamine in lower doses otherwise nonlytic; the sensitizing action also resulted in the extension of protamine bacteriolytic pattern including several staphylococcal strains; higher bacteriolytic doses of protamine were contrastively unable to lyse OsO? prefixed cells and gave an inconstant lytic value with formaldehyde treated bacteria. With higher concentrations, 0 s 0 4 preserved intactly its sensitizing action while formaldehyde displayed a decrease in its ability to sensitize B. subtilis cells to the lytic effect of protamine. Scaning electron microscopy of polycation treated cells showed prelytic lesions as surface granulations, shape and size modifications and cell splits. The interpretation of the results in terms of intra-and intermolecular adducts accompanied by con­ formational changes in surface macromolecules is discussed. It is concluded that the results match the model of polycation bacteriolysis by wall multizonal picnosis leading to surface splits and thereby triggering cell-lysis. 
  Reference    Z. Naturforsch. 35c, 805—810 (1980); received July 9 1980 
  Published    1980 
  Keywords    Poly-L-arginine, Protamine, Bacillus subtilis, Staphylococcus aureus, Glutaraldehyde 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0805.pdf 
 Identifier    ZNC-1980-35c-0805 
 Volume    35