Experimental and Molecular Docking Studies on the Interaction of a Water-Soluble Pd(II) Complex Containing β-Amino Alcohol with Calf Thymus DNA

Unveiling the promising anticancer activity of palladium(II)-aryl complexes bearing diphosphine ligands: a structure-activity relationship analysis

In continuation of our previous works on the cytotoxic properties of organopalladium compounds, in this contribution we describe the first systematic study of the anticancer activity of Pd(II)-aryl complexes. To this end, we have prepared and thoroughly characterized a wide range of palladium derivatives bearing different diphosphine, aryl and halide ligands, developing, when necessary, specific synthetic protocols. Most of the synthesized compounds showed remarkable cytotoxicity towards ovarian and breast cancer cell lines, with IC50 values often comparable to or lower than that of cisplatin. The most promising complexes ([PdI(Ph)(dppe)] and [PdI(p-CH3-Ph)(dppe)]), characterized by a diphosphine ligand with a low bite angle, exhibited, in addition to excellent cytotoxicity towards cancer cells, low activity on normal cells (MRC5 human lung fibroblasts). Specific immunofluorescence tests (cytochrome c and H2AX assays), performed to clarify the possible mechanism of action of this class of organopalladium derivatives, seemed to indicate DNA as the primary cellular target, whereas caspase 3/7 assays proved that the complex [PdI(Ph)(dppe)] was able to promote intrinsic apoptotic cell death. A detailed molecular docking analysis confirmed the importance of a diphosphine ligand with a reduced bite angle to ensure a strong DNA-complex interaction. Finally, one of the most promising complexes was tested towards patient-derived organoids, showing promising ex vivo cytotoxicity.

Analysis of the binding mechanism for a water-soluble Pd(II) complex containing β-amino alcohols with HSA applying experimental and computational methods

In the study ahead, the binding interactions of the [Pd (HEAC) Cl2] complex with human serum albumin (HSA) protein have been assayed in vitro (pH= 7.40) utilizing computational and experimental procedures. The mentioned complex was synthesized as a water-soluble complex from {2-((2-((2-hydroxyethyl)amino)ethyl)amino) cyclohexanol} ligand = HEAC. The results of electronic absorption and circular dichroism investigations illustrated that the hydrophobicity of the Tryptophan microenvironment in HSA undergoes the changes by binding to the Pd(II) complex without substantial perturbations on the protein secondary structure. The fluorescence emission spectroscopy analysis revealed that with rising temperature, the quenching constant (Ksv) in the Stern-Volmer's relation decreases; so, it can be said that the interaction process is along with a static quenching mechanism. The values of 2.88 × 105 M-1, and 1.26 represent the binding constant (Kb) and the number of the binding sites (n), respectively. The Job graph showed the maximum point at χ = 0.5, which means organizing a new set with 1:1 stoichiometry. Thermodynamic profile (ΔH < 0, ΔS < 0, and ΔG < 0) has affirmed that van der Waals forces and hydrogen bonds have a basic function in the Pd(II) complex-albumin bindings. The ligand-competitive displacement studies utilizing warfarin and ibuprofen have represented that Pd(II) complex interacts with albumin by site II (subdomain IIIA). The computational molecular docking theory approved the results of the site-competitive tests; also, it indicated the existence of hydrogen bonds and van der Waals forces in Pd(II) complex-albumin interactions.Communicated by Ramaswamy H. Sarma.

Interaction studies of water-soluble Zn(II) complex with calf thymus DNA using biophysical and molecular docking methods"

The binding between a fluorescent water-soluble Zn(II) complex of {2-[N-(2-hydroxyethylammonioethyl) imino methyl] phenol} and calf thymus DNA (ct-DNA) was investigated using spectroscopic techniques. The complex was prepared and identified by FT-IR, and 1H NMR spectroscopies. The significant changes in the absorption and the circular dichroism spectra of ct-DNA in the presence of the Zn(II) complex implied the interaction between the Zn(II) complex and ct-DNA. Upon addition of ct-DNA, the fluorescence emission intensity of the Zn(II) complex was increased and indicated the interaction between the Zn(II) complex and ct-DNA was occurred. The binding constant values (Kb) resulted from fluorescence spectra clearly showed the Zn(II) complex affinity to ct-DNA. The fluorescence studies also approved the static enhancement mechanism in the Zn(II) complex-DNA complexation process. The thermodynamic profile exhibited the exothermic and spontaneous formation of ct-DNA-Zn(II) complex system via hydrogen bonds and van der Waals forces. The competitive fluorescence investigation by methylene blue (MB), and Hoechst 33258 demonstrated that the Zn(II) complex could replace the DNA-bound Hoechst and bind to the minor groove binding site in ct-DNA. The viscosity changes were negligible, representing the Zn(II) complex binding to DNA via the groove binding mode. Molecular docking simulation affirmed that the Zn(II) complex is located in the minor groove of ct-DNA near the DG12, DA17, DA18, and DG16 nucleobases.

In Vitro and Computational Approaches to Untangle the Binding Mechanism of Galangin with Calf Thymus DNA

Flavonoids have potential applications in the nutraceutical, medicinal, pharmaceutical and cosmetic fields. The binding of flavonoids with DNA could unravel essential information required for the design of novel and effective chemical agents. The present paper describes the interaction of a flavonoid and a potent anticancer drug, galangin (GAL) with calf thymus DNA (ct-DNA) by fluorescence, UV absorption, melting studies, viscosity measurements and molecular docking studies. A hyperchromic effect was noticed in the absorption spectra of ct-DNA in the presence of the GAL system, indicating the presence of a groove mode of binding. Furthermore, GAL persuaded the minor changes in ct-DNA viscosity, indicating a non-intercalative mode of binding. Fluorescence studies revealed that the GAL quenched the fluorescence intensity of ct-DNA-Hoechst, thereby indicating the interaction between GAL and ct-DNA. Fluorescence results obtained at 298, 308 and 318 K revealed that the fluorescence quenching of ct-DNA-Hoechst-GAL occurred through the static quenching mechanism. Thermodynamic parameters for ct-DNA-Hoechst-GAL were computed and suitable conclusions were drawn. The changes noticed in the conformation of ct-DNA upon interaction with GAL were evaluated in terms of molar ellipticity. It indicated a plausible interaction between ct-DNA and GAL. The molecular docking studies also confirmed the groove mode of binding in the ct-DNA-GAL system. Thus, this work helped to unravel the binding mechanism between GAL and ct-DNA.

Nickel-Metformin Ternary Complexes: Geometrical, Thermal, DNA Binding, and Molecular Docking Studies

Novel three nickel(II) complexes of type [Ni(metf)(o-phen)₂]Cl₂ (1), [Ni(metf)(opda)₂]Cl₂ (2), [Ni(metf)(2-2'bipy)₂]Cl₂ (3), (Metf = metformin, o-phen = ortho-phenanthroline, opda = ortho-phenylenediamine, 2-2' bipy = 2-2' bipyridyl) were synthesized and characterized by various analytical and spectral techniques. Based on these studies, octahedral geometry is assigned to these complexes. The DNA binding properties of these complexes were investigated by absorption, emission, and viscosity studies. From the spectral data, it was concluded that the complexes bind to DNA through groove mode of binding. The intrinsic binding constants (K_b) from absorption spectroscopy were 1.60 × 10⁴, 3.57 × 10⁴, and 5.70 × 10⁴ M^-1 for 1, 2, and 3, respectively, and Stern-Volmer quenching constants (K_sv) from emission spectroscopy were 0.11, 0.87, and 0.24, respectively. Thermal degradation pattern of the compounds was studied and Coats-Redfern method is used to determine kinetic parameters for complexes 1, 2, and 3 from thermal studies. The software Discovery Studio 2.1 was used to assess the binding affinity and interaction pattern of complexes with the B-DNA receptor protein and complex 1 has the highest dock score.