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1Author    Hartmut Schmidt, Axel LaßmannRequires cookie*
 Title    ESR-Untersuchungen zur Photochemie des Acridinorange ESR Investigations on the Photochemistry of Acridine Orange  
 Abstract    Acridinfarbstoffe werden in photochemischen und photobiologischen Reaktionen häufig als Sensibilisa­ toren eingesetzt. Im Falle der photodynamischen Desaktivierung von Lysozym in Gegenwart von Acri­ dinorange konnten wir zeigen *, daß der elektronisch angeregte Farbstoff Sauerstoff in den Singulett-zustand 1Ag überführt, der dann weiter mit dem Enzym reagiert. Im Verlauf der photodynamischen Reaktion wird jedoch auch der Farbstoff teilweise zerstört. Die Kinetik der Farbstoffbleichung läßt sich nicht allein auf der Grundlage des von uns postulier­ ten Reaktionsschemas verstehen 2. Von vielen Farbstoffen ist bekannt, daß bei Ein­ strahlung in die langwelligste Absorptionsbande intermediär semioxidierte und/oder semireduzierte Photoprodukte entstehen. Derartige radikalische Zwischenprodukte wurden blitzlichtspektroskopisch auch für Acridinorange nachgewiesen 3' 4 und müs­ sen bei einer detaillierteren Beschreibung des photo­ dynamischen Reaktionsverlaufs sicherlich berück­ sichtigt werden. Zum Nachweis derartiger Zwischenprodukte sollte die ESR-Spektroskopie besonders geeignet sein, da über die Hyperfeinstruktur unmittelbar Rück­ schlüsse auf die Struktur der Radikale möglich sind5. Die Anwendung dieser Methode scheitert meistens daran, daß bei kontinuierlicher Bestrah­ lung von Farbstofflösungen bei Zimmertemperatur die stationäre Konzentration der radikalischen Zwi­ schenprodukte unterhalb der Nachweisgrenze der herkömmlichen ESR-Spektrometer liegt. Diese Schwierigkeiten lassen sich durch Zusatz geeigneter Substanzen ("Spinfänger") umgehen, die mit kurz­ lebigen Radikalen unter Bildung langlebiger Sekun­ därradikale ("Spinaddukte") reagieren. Die primär gebildeten Zwischenprodukte lassen sich auf diese Weise auf Grund der Hyperfeinstruktur der Spin­ addukte identifizieren 6. 
  Reference    (Z. Naturforsch. 29c, 301—302 [1974]; eingegangen am 26. Februar 1974) 
  Published    1974 
  Keywords    Acridine Orange, ESR, Spin Trap, Nitromethane, Hydrogen Addition 
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 TEI-XML for    default:Reihe_C/29/ZNC-1974-29c-0301_n.pdf 
 Identifier    ZNC-1974-29c-0301_n 
 Volume    29 
2Author    I. Basic, KineticsHartmut Schmidt, Peter RosenkranzRequires cookie*
 Title    On the Mechanism of the Acridine Orange Sensitized Photodynamic Inactivation of Lysozyme  
 Abstract    The kinetics of the photodynamic desactivation of lysozyme in presence of acridine orange as the sensitizer have been investigated in detail varying oxygen, protein, dye concentration, ionic strength and pH value. The kinetics can be approximately described as an over all pseudo-first-order rate process. Changing the solvent from water to D20 or by quenching experiments in pres­ ence of azide ions it could be shown that the desactivation of lysozyme is caused exclusively by singlet oxygen. The excited oxygen occurs via the triplet state of the dye with a rate constant considerably lower than that to be expected for a diffusionally controlled reaction. Singlet oxygen reacts chemically (desactivation, k —2.9 x 107 M -1 sec-1) and physically (quenching process, k = 4.1 x 108 m — 1 sec-J) with the enzyme. The kinetical analysis shows that additional chemical reac­ tions between singlet oxygen and lysozyme would have only little influence on the kinetics of the desactivation as long as their products would be enzymatically active and their kinetical constants would be less than about 1 x 1 0 8 m -1 sec-1. 
  Reference    (Z. Naturforsch. 31c, 29 [1976]; received July 7/September 19 1975) 
  Published    1976 
  Keywords    Photodynamic Effect, Singlet Oxygen, Lysozyme, Acridine Orange, Kinetics 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0029.pdf 
 Identifier    ZNC-1976-31c-0029 
 Volume    31 
3Author    Harald Wille, JürgenP. Auluhn, H. Erbert, W. Z. Im, M. Erm AnnRequires cookie*
 Title    Bindungskonstanten, Bindungsenthalpien und Entropien für die nicht-kompetitive und die kompetitive Bindung von Acriflavin, Tetramethylacriflavin und Acridinorange an DNA Binding Constants, Binding Enthalpies and Entropies of the N on-Com petitive and the Competitive Binding o f A criflavine, Tetram ethylacriflavine and Acridine Orange to DNA  
 Abstract    The binding of the dye cations acriflavine AF, tetramethylacriflavine TMAF and acridine orange AO (scheme of structures) to calf thymus DNA has been investigated by means of absorption spectroscopy, Table I. In order to avoid dye association we used very low dye concen­ trations and sufficiently high DNA concentrations. In this case we got linear Scatchard isotherms. The formal Scatchard binding constant K strongly depends on the salt concentration Cs (S = NaCl) of the solution and the temperature T (278-303 K), £ (C S, T). The average value of binding sites per mononucleotide is n = 0.17. It is independent of the dye species and of Cs and T. The value of r (bound dye cations per mononucleotide) diminishes with growing salt concentra­ tion CS(CS< 1 m). At sufficiently high salt concentrations r is approximately constant (Cs > 1 m). Obviously there are two types of binding of the dye cations to DNA even in the domain of linear Scatchard isotherms. They can be distinguished experimentally with the competitive salt effect. To describe r(C s ,T) or K (C s , T) we used a simple model with three equilibria: 1. Non­ competitive binding 1 (intercalation) of dye cations to n1 CN binding sites (CN = concentration of mononucleotides), equilibrium constant K 1. 2. Competitive binding 2 (external binding) of dye cations to n2 CN binding sites, equilibrium constant K 2. In contrast to type 1 binding, the dye cations in type 2 binding can be replaced by metal cations M of S (M = Na®) at sufficiently high salt concentrations Cs . 3. Competitive binding 3 of M to the same sites of 2 and the dye cations as competitor, equilibrium constant K 3. The model agrees very well with the experiments on the condition «} = n2 = n. Therefore the dye can be bound to one of the n CN binding sites either non-competitively or competitively. Type 1 and type 2 binding exclude one another at the same binding site in the domain of linear Scatchard plots. The binding constants K i(i = 1, 2, 3) have been determined by means of the competitive salt effect, Table II. They only are T dependent. From K (T)\ we got the binding enthalpies AfT> and binding entropies AS?, Table III. AF and AO cations are bound non-competitively and competitively, TMAF only competi­ tively. In comparison with AF or AO the competitive binding of TMAF is much weaker. In the case of AF and AO K 1 is approximately one power of ten smaller than K2,K1 < K 2\ The binding enthalpies of the non-competitive and the competitive binding are nearly equal, AH\ = AH*2. Therefore the difference in the binding constants K lt K 2 can be attributed to the difference in the binding entropies, Thermodynamically type 2 binding (external binding) is preferred to type 1 binding (intercalation). The binding enthalpy of Na® to DNA is in all cases nearly zero, AH\ ^ 0. Only the increase of entropy > 0 enables binding 3. From the thermodynamic data follows that type 1 and type 2 binding of AF and AO are produced by electrostatic and hydrophobic interaction which are intensified by hydrogen bonding. In contrast to this the weaker competitive binding of TMAF is caused by electrostatic and hydrophobic interaction only. Our investigations agree with former works on ethidium bromide E and tetramethylethidium bromide TME (scheme of structures, Tables II and III). They are consistent with the assignment non-competitive binding = intercalation, competitive binding = external binding. Sonderdruckanforderungen an Prof. Dr. H. Zimmermann. 0341-0382/82/0500-0413 $01.30/0 414 H. Wille et al. ■ Bindung von Acriflavin, Tetramethylacriflavin und Acridinorange an DNA 
  Reference    Z. Naturforsch. 37c, 413—427 (1982); received February 26 1982 
  Published    1982 
  Keywords    Dye Binding to DNA, Intercalation, External Binding, Binding Constants, Binding Enthalpies, Binding Entropies, Acriflavine, Tetramethylacriflavine, Acridine Orange 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0413.pdf 
 Identifier    ZNC-1982-37c-0413 
 Volume    37