Spectroscopic studies of the interaction of bichromophoric cyanine dyes with DNA. Effect of ionic strength

• Published in: Biochimica et biophysica acta Vol. 1621; no. 2; pp. 183 - 191
• Main Authors: Schaberle, Fábio A., Kuz'min, Vladimir A., Borissevitch, Iouri E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 02.05.2003
• Subjects: Bichromophoric cyanine dye; Carbocyanines - chemistry; Chromogenic Compounds - chemistry; Circular Dichroism; DNA; DNA - chemistry; Ionic strength; Osmolar Concentration; Photochemotherapy; Photodynamic therapy; Sodium Chloride - pharmacology; Spectrometry, Fluorescence; Photodynamic therapy; Ionic strength; DNA; Bichromophoric cyanine dye
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/S0304-4165(03)00057-6

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 ( ε=1.33×10 5 M −1 cm −1) and weak fluorescence ( ϕ 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 ϕ fl=0.05 and bound monomers by ϕ 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.