Spectroscopic studies of the interaction of bichromophoric cyanine dyes with DNA. Effect of ionic strength.
Spectroscopic characteristics of a cyanine dye with two chromophores (biscyanine dye, BCD) in aqueous solutions and effects of NaCl and DNA upon these characteristics have been studied by optical absorption, circular dichroism (CD) and fluorescence spectroscopies. In homogeneous solutions, BCD is characterized by intense optical absorption (epsilon =1.33 x 10(5) M(-1) x cm(-1)) and weak fluorescence (phi(fl)=0.018) in the wavelength region greater than 600 nm. The dye forms H-aggregates at low concentrations (10(-6) M). NaCl stimulates the formation of both H- and J-aggregates of the dye at much lower dye concentrations, while DNA in low concentrations (<10(-6) M) stimulated the formation of just J-aggregates on the surface of the DNA molecule. Higher DNA concentrations induce the dye to disaggregate, and there exists an equilibrium between three dye forms: free monomers, J-aggregates and bound monomers, the maximum content of J-aggregates was observed at [DNA]/[BCD]=0.6+/-0.2 and total disaggregation at [DNA]/[BCD]=190+/-20. J-aggregates are characterized by phi(fl)=0.05 and bound monomers by phi(fl)=0.44. In the presence of NaCl, total disaggregation was observed at [DNA]/[BCD]=570+/-10 due to competition between Na(+) and the dye molecules for DNA electronegative binding sites.
Departamento de Fi;sica e Matemática, Faculdade de Filosofia Ciência e Letras de Ribeirão Preto, Universidade de São Paulo, Av Bandeirantes 3900, Vila Monte Alegre, CEP 14040-901, Ribeirão Preto SP, Brazil.
Fábio A
FA
Schaberle
Vladimir A
VA
Kuz'min
Iouri E
IE
Borissevitch
D002232:Carbocyanines / Q000737:chemistry*; D002863:Chromogenic Compounds / Q000737:chemistry*; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D009994:Osmolar Concentration; D010778:Photochemotherapy; D012965:Sodium Chloride / Q000494:pharmacology; D013050:Spectrometry, Fluorescence
D002232:Carbocyanines; D002863:Chromogenic Compounds; D012965:Sodium Chloride; D004247:DNA