Microcalorimetry of interaction of dihydro-imidazo-phenanthridinium (DIP)-based compounds with duplex DNA

Biophysical studies on the base specificity and energetics of the DNA interaction of photoactive dye thionine: Spectroscopic and calorimetric approach

“…First of all, the values of ΔCp are non-zero indicating temperature dependence of the enthalpy change. Secondly, the values of ΔCp in almost all cases fall within the range of 100-500 cal/mol K or are very close to the lower limit that is frequently observed for both ligand-nucleic acid and ligand-protein interaction [47,48]. The higher values of ΔCp for thionine binding to ML DNA compared to others most likely suggest substantial conformational change in this DNA structure that was reflected in circular dichroic study as well.…”

“…The free energy contribution from the hydrophobic transfer step of binding of these molecules may be calculated from the relationship [50], ΔG hyd =80(±10) × ΔCp. The ΔG hyd values for thionine binding to CP, HT and ML DNAs were deduced to be −8.1, −10.7 and −16.7 kcal/mol, that are well within the range that was observed for typical intercalating DNA and RNA intercalating molecules [21,24,36,42,44,48,51].…”

“…Therefore, the slightly negative and non-zero ΔCp values that were observed for thionine-DNA complexation appear to denote structure specific binding. Generally, for DNA intercalators and groove binding molecules a large hydrophobic contribution to the binding free energy is expected due to their aromatic ring system and binding should be energetically favourable [48]. The free energy contribution from the hydrophobic transfer step of binding of these molecules may be calculated from the relationship [50], ΔG hyd =80(±10) × ΔCp.…”

DNA binding of benzophenanthridine compounds sanguinarine versus ethidium: Comparative binding and thermodynamic profile of intercalation

“…NaCl molarity (mM) small molecules to macromolecules [39][40][41][42][43][44]. Figure 3a and b (upper panels) shows the representative raw ITC profiles resulting form the titration of SNC and EB with CT DNA.…”

Interaction of Isoquinoline Alkaloid Palmatine with Deoxyribonucleic Acids: Binding Heterogeneity, and Conformational and Thermodynamic Aspects

“…where f is the extent of counterion binding for phosphate residue before ligand association, and that value is inversely proportional to the distance between the phosphate, and it is in the range of 0.88 -1.24 for a normal duplex DNA -ligand intercalation complex [27] [28]. K o is the value of the binding constant at 1m [Na þ ] and is assumed to be free of electrostatic components.…”