The influence of GC/AT composition on intercalating and semi-intercalating binding of ethidium bromide to DNA

• Autor(a) principal: Vardevanyan,Poghos O.
• Data de Publicação: 2012
• Outros Autores: Antonyan,Ara P., Parsadanyan,Marine A., Shahinyan,Mariam A., Hambardzumyan,Lilit A., Torosyan,Margarita A., Karapetian,Armen T.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532012001100009
• topic: DNA; ethidium bromide; adsorption isotherms; spectrophotometry; spectrofluorometry

The binding parameters of ethidium bromide (EtBr) with DNA of various GC/AT ratios were determined using absorption and fluorescence spectroscopy. Our experimental data clearly demonstrate the co-existence of fluorescing and non-fluorescing types of "strong" binding at low concentration of EtBr. The fluorescent complex corresponds to the ordinary intercalative model. The non-fluorescent complex is referred to semi-intercalative binding of EtBr. The binding constant (K) and the number of base pairs corresponding to a binding site (n) of the fluorescent (Kf and n f) and non-fluorescent (Knf, n nf) types of interactions were determined. The average size of binding site (n) is equal to 1.5 bp (absorption spectroscopy), and n f ca. 2 bp (fluorescence spectroscopy). It was shown that n nf is dependent on GC-content and total n is independent of it.