A fluorescent complex between ethidium bromide and nucleic acids. Physical-chemical characterization |
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| Authors: | J B LePecq C Paoletti |
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| Affiliation: | 1. Young Researchers and Elite Club, East Tehran Branch, Islamic Azad University, Tehran, Iran;2. Department of Chemistry, Faculty of Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran;3. Laboratory of Green Chemistry, Lappeenranta University of Technology, Jääkärinkatu 31, FI-50100 Mikkeli, Finland;4. Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran;5. Department of Chemistry, Shahid Beheshti University, Tehran, Iran;6. Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia;1. Department of General and Inorganic Chemistry, Faculty of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece;2. Department of Nutrition and Dietetics, Faculty of Food Technology and Nutrition, Alexandrion Technological Educational Institution, Sindos, Thessaloniki, Greece;1. Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary;2. MTA-SZTE Bioinorganic Chemistry Research Group, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary;3. Centro de Química e Bioquímica (CQB), Faculdade de Ciências, ULisboa, Campo Grande, Lisbon, Portugal;4. Centro de Química Estrutural (CQE), Faculdade de Ciências, ULisboa, Campo Grande, Lisbon, Portugal;5. Centro de Química Estrutural (CQE), Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1, Lisbon, Portugal;6. Centro de Ciências e Tecnologias Nucleares (C2TN), Instituto Superior Técnico, ULisboa, Estrada Nacional 10, Bobadela, Loures, Portugal;7. Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Quinta da Granja, Monte da Caparica, Portugal;1. Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, Splaiul Independentei 202, Bucharest 060021, Romania;2. Department of Physical Chemistry, University of Bucharest, Blvd. Elisabeta 4-12, Bucharest 030018, Romania |
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| Abstract: | At high salt concentrations, ethidium bromide (EB) is shown to form a fluorescent complex with helical polynucleotides which has a strikingly enhanced fluorescence quantum yield. In this paper we present evidence that formation of this complex (complex I) ia specific for base-paired regions either in DNA, RNA or RNA: DNA hybrids, and that the basis of this specificity is intercalation of the dye between base pairs. At low salt concentrations a second mode of binding EB3 (as complex II) is observed: it appears to be electrostatic binding of the cationic dye to negatively charged phosphate groups. Complex II can be distinguished readily from complex I by its fluorescence properties. The nature of the DNA binding sites for EB has been investigated by: (a) measurement of their number, and dependence of the binding on pH and salt concentration, as well as on the secondary structure and GC content of the DNA; (b) study of the energy transfer from DNA to EB; (c) studies of competition for DNA between EB and Na+, Mg2+, quinacrine and actinomycin, and (d) characterization of complex I by flow dichroism, thermal melting curves and buoyant density. |
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