Studies on Interaction of Safranine T with Herring Sperm DNA in γ−Cyclodextrin

Abstract

Purpose: In order to understand the reaction mechanism and provide guidance for the application of organic dyes targeted to DNA, the interactions of Safranine T (ST) in γ− cyclodextrin (γ−CD) with herring sperm DNA were explored in physiological buffer (pH 7.40). Method: The resultant inclusion compounds were characterized by fluorescence spectra, powder X−ray diffraction, and FT−IR spectroscopy. Results: The results confirmed the existence of 1:1 inclusion complex of ST with γ−CD. Fluorescence spectra were employed to understand the binding of γ−cyclodextrin−safranine T (γ−CD−ST) with DNA. The binding ratio of γ−CD−ST with DNA is n γ−CD−ST :n DNA = 9:1. The thermodynamic parameter elucidated that the binding was exothermic, driven mainly by enthalpy. As acridine orange (AO) presumably binds initially to DNA by intercalation, AO was employed in the study. Competitive interaction of γ−CD−ST and AO with DNA suggested γ−CD−ST substituted for AO in the DNA–AO system, that means there exist intercalation binding. The influence of A, T, C, G to γ−CD−ST showed g-CD-ST mainly acted on the A–T enrichment regions of the DNA. The relative viscosity of DNA further suggested there exist a partial non-classical intercalation binding. From Scatchard method, we can confirm that there are groove and intercalation binding between g-CD-ST and DNA. Conclusion: The results taken together suggested the interactions of γ−CD−ST with DNA are intercalation and groove binding