Microcalorimetry and binding studies of DNA upon interaction with [pyridine diamine] 2[Co(phenanthroline dicarboxylate) 2]

• Published in: Thermochimica acta Vol. 428; no. 1; pp. 157 - 163
• Main Authors: Nazari, K., Golchin, A.R., Moosavi-Movahedi, A.A., Saboury, A.A., Hakimelahi, G.H., Shockravi, A., Tangestani-nejad, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-04-2005; Elsevier Science
• Subjects: [pyda] 2[Co(phendc) 2]; Binding analysis; Biological and medical sciences; DNA; Enthalpy; Fundamental and applied biological sciences. Psychology; Interactions. Associations; Intermolecular phenomena; Ionization; Microcalorimetry; Molecular biophysics; Unfolding; [pyda] 2[Co(phendc) 2]; Ionization; DNA; Enthalpy; Binding analysis; Unfolding; Microcalorimetry; Cobalt Complexes; Transition element complexes; Denaturation; Organic ligand; Molecular interaction; Potentiometry; Enthalpy: Binding analysis; Pyridine derivatives; Diamine; [pyda]2[Co(phendc)2]; Thermal analysis; Thermodynamic properties
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2004.10.008

The interaction of calf thymus DNA with [pyridine diamine]
2[Co(phenanthroline dicarboxylate)
2], [
pyda]
2[
Co(
phendc)
2], complex has been studied at 10
mM phosphate buffer at 27
°C, pH 7.0 using various techniques including isothermal titration calorimetry (ITC), UV–vis spectrophotometry and potentiometric titration. Sigmoidal absorption profile implies the existence of cooperative interactions between DNA and [pyda]
2[Co(phendc)
2] that induces a conformational change in DNA structure. Scatchard plots confirm this cooperative interaction. The calorimetric enthalpy curve of [pyda]
2[Co(phendc)
2] upon interaction with DNA is measured by ITC. The enthalpy of binding (Δ
H
bin) of [pyda]
2[Co(phendc)
2] with DNA is also obtained spectrophotometrically by determining of equilibrium binding constants at 27 and 37
°C based on Wyman binding potential and van’t Hoff relation. The enthalpy of ionization (Δ
H
ion) is also obtained by acid–base titration at 27 and 37
°C in 100
mM KCl solution using modified differential van’t Hoff relation for estimation of (Δ
H
ion). The binding data was analyzed in a two-set binding sites model based on the Hill equation. The first phase of the calorimetric enthalpy curve is consistent with a first set of binding sites and further phases are consistent with a second set of binding sites.