Spectroscopic Studies of DNA Interactions with Food Colorant Indigo Carmine with the Use of Ethidium Bromide as a Fluorescence Probe

Abstract

The interaction of indigo carmine (IC) with calf thymus DNA in physiological buffer (pH 7.4), using ethidium bromide (EB) dye as a fluorescence probe, was investigated by ultraviolet-visible absorption, fluorescence, and circular dichroism (CD) spectroscopy, coupled with viscosity measurements and DNA-melting studies. Hypochromicity of the absorption spectra of IC and enhancement in fluorescence polarization of IC were observed with the addition of DNA. Moreover, the binding of IC to DNA was able to decrease iodide and single-stranded DNA (ssDNA) quenching effects, increase the melting temperature and relative viscosity of DNA, and induce the changes in CD spectra of DNA. All of the evidence indicated that IC interacted with DNA in the mode of intercalative binding. Furthermore, the three-way synchronous fluorescence spectra data obtained from the interaction between IC and DNA-EB were resolved by parallel factor analysis (PARAFAC), and the results provided simultaneously the concentration information and the pure spectra for the three reaction components (IC, EB, and DNA-EB) of the system at equilibrium. This PARAFAC demonstrated that the intercalation of IC molecules into DNA proceeded by substituting for EB in the DNA-EB complex. The calculated thermodynamic parameters, ΔH° and ΔS°, suggested that both hydrophobic interactions and hydrogen bonds played a predominant role in the binding of IC to DNA.

Intercalation binding of food antioxidant butylated hydroxyanisole to calf thymus DNA

“…The melting temperature (T m ) of pure ctDNA and BHA-ctDNA complex were obtained from the transition midpoint of the melting curves based on f ss versus temperature (T) according to the equation [16]: where A, A 0 and A f represent the absorbance intensity at the corresponding temperature, the initial and final absorbance intensity, respectively.…”

“…Usually, the non-intercalative (e.g. groove or electrostatic) binding of small molecules with DNA causes insignificant change in T m , whereas an obvious increase in T m (5-8°C) could be observed for the strong intercalation interaction [16]. The melting experiments were performed to monitor the change in T m for ctDNA in the absence and presence of BHA to investigate the binding properties between BHA and ctDNA.…”

“…Many studies regarding the interactions between DNA and harmful chemicals have been reported, such as pyriproxyfen [9], permethrin [10], clodinafoppropargyl [11], diquat [12], salbutamol [13], ractopamine [14], and heavy metal ions [15]. In recent years, some food additives such as dyes [16][17][18] and sweeteners [19,20] bound to DNA were also investigated. These studies are valuable for exploring the structural and functional features of the biomacromolecule to decipher its biophysical processes [21], and can provide useful information for further understanding the toxicology of the chemicals.…”

Synthesis of a novel 4H-pyran analog as minor groove binder to DNA using ethidium bromide as fluorescence probe

“…It is the carrier of hereditary information and involved in the biological synthesis of enzymes and proteins via transcription and replication [1,2]. DNA is most important cellular target for many natural and synthetic organic molecules, especially, anticancer and antiviral drugs [3][4][5].…”

“…DNA is most important cellular target for many natural and synthetic organic molecules, especially, anticancer and antiviral drugs [3][4][5]. Binding of small molecules with DNA is very important for designing low-toxic drugs for clinical use [1] because the binding modes and binding properties during the interaction can help us to understand the functional mechanism of drugs and provide theoretical background for the development of new drugs targeted to DNA [3][4][5]. Therefore, studying the interaction of DNA is of prime importance in drug design and development process.…”