Exploring the interaction between calf thymus DNA and 11H-Indeno[1,2-b]quinoxalin-11-one Thiosemicarbazones: Spectroscopies and in vitro antitumor activity

Understanding the interactions between small molecules and calf thymus deoxyribonucleic acid (ctDNA) is critical for certain aspects of drug discovery. In this study, three 11H-indeno[1,2-b]quinoxalin-11-one thiosemicarbazones were synthesized and their interaction with ctDNA was examined through various spectroscopic techniques, including ultraviolet (UV) spectroscopy, fluorescence spectroscopy, and circular dichroism (CD) spectrum, and through physicochemical methods, including viscosity measurements. In addition, the effects of these thiosemicarbazone compounds 4a, 4b and 4c on several cancer cell lines were explored. The results of UV absorption, fluorescence quenching and CD experiments indicated that compounds 4a, 4b and 4c primarily bound to ctDNA by an intercalation. This mode of interaction was further corroborated by viscosity measurements. Docked poses of compound 4a revealed that it formed a crucial N position hydrogen bond with the DNA receptor. The chemical structure of compound 4a was further confirmed by X-ray crystallographic analysis. Through biological evaluation, it was found that the in vitro cytotoxicity of three compounds agreed with the order of their binding strength to ctDNA, indicating that the antitumor activity of these compounds correlated with their binding affinity to ctDNA.

New lanthanum (III) complexes containing azaphosphor β-diketon and diimine ligands: Synthesis, crystallography, morphology properties, DNA binding, DNA cleavage, and DFT calculation

Two octa-coordinated lanthanum (III) complexes of deprotonated azaphosphor β-diketon and diimine ligands, [LnL3Q] (L = [Cl2CHC(O)NP(O)(NC6H12)2], Q = Phen (C1) and Bipy (C2)), were synthesized and characterized by elemental analysis, IR, and NMR spectra. X-ray crystallography revealed a distorted tetragonal antiprism LaO6N2 coordination geometry around the lanthanum atom in both compounds. Nano-sized complexes (Ć1 and Ć2) were synthesized via a sonochemical process and analyzed using SEM and XRPD. TGA-DTA analysis were performed on complexes in both bulk and nano scales. Redox behavior was also examined by cyclic voltammetry. The interaction between the complexes and calf thymus DNA (ct-DNA) was investigated using UV-Vis spectroscopy, fluorescence titration, viscosity measurements, and gel electrophoresis. C2 and Ć2 likely intercalate between DNA base pairs through van der Waals forces and hydrogen bonding, whereas C1 and Ć1 interact with DNA via groove binding. Further, result indicated the apparent association constant (Kapp) in the range of 4.53 × 104 M-1-26.86 × 104 M-1 with the highest value for nanocomplex Ć2. Fluorescence studies revealed dynamic and static quenching for C1, while the other compounds followed a static quenching process. Hirshfeld surface analysis and the NCI method were employed to demonstrate how non-covalent interactions influence the crystal packing through intermolecular interactions.

Anticancer Activity Assessment and DNA Binding Properties of Two Binuclear Platinum (II) Complexes using Spectroscopic and Molecular Simulation Approaches

BACKGROUND

Nowadays, the biological properties and anticancer activities of platinum-based drugs and metal coordination complexes have been receiving particular attention. These compounds have revealed clinical potential in cancer chemotherapy.

OBJECTIVE

In this research, two binuclear platinum complexes including [Pt2Cl2(bhq)2(μ-dppm)] (1) and [(p- MeC6H4)(bhq) Pt(μ-dppm)Pt(bhq)(CF3CO2)] (2) with bhq: benzo[h] quinolone and dppm: bis(diphenylphosphino) methane have been synthesized and evaluated for their anticancer activity against A2780 and A2780/RCIS cancer cell lines.

METHODS

The DNA binding and interaction of AMP/GMP nucleotide with these complexes were explored by several experimental and theoretical methods, including UV-Visible, fluorescence spectroscopic techniques and docking analysis. These complexes have demonstrated significant anticancer properties against cisplatinsensitive (A2780) and cisplatin-resistant (A2780/RCIS) human ovarian cancer cell lines.

RESULTS

The obtained results indicated that these complexes interact with DNA. Additionally, the fluorescence emission measurements indicated that the platinum complexes binding with DNA structure occurs through nonintercalative interaction. The molecular docking assessments have also revealed the binding of these platinum complexes through DNA grooves. Moreover, the results have indicated that complex 1 exhibited more anticancer activity than complex 2.

CONCLUSION

The results of the DNA binding with these platinum complexes confirmed their potential antitumor properties. The substitution of -C6H4CH3 and -CO2CF3 groups in complex 2 with two chlorine atoms in complex 1 acquired the significant improvement of the anticancer activity against the cancer cell.

Assessment on the binding characteristics of dasatinib, a tyrosine kinase inhibitor to calf thymus DNA: insights from multi-spectroscopic methodologies and molecular docking as well as DFT calculation

The binding characteristics of calf thymus DNA (ct-DNA) with dasatinib (DSTN), a tyrosine kinase inhibitor was assessed through multi-spectroscopic methodologies and viscosity measurement combined with molecular docking as well as DFT calculation to understand the binding mechanism, affinity of DSTN onto ct-DNA, effect of DSTN on ct-DNA conformation, and among others. The results confirmed DSTN bound onto ct-DNA, leading to forming the DSTN-ct-DNA complex with the binding constant of 4.82 × 10³ M^-1 at 310 K. DSTN preferentially inserted to the minor groove of ct-DNA with rich A-T region, that was the binding mode of DSTN onto ct-DNA was groove binding. The enthalpic change (ΔH⁰) and entropic change (ΔS⁰) during the binding process of DSTN with ct-DNA were 128.9 kJ mol^-1 and 489.2 J mol^-1 K^-1, respectively, confirming clearly that the association of DSTN with ct-DNA was an endothermic process and the dominative driven-force was hydrophobic interaction. Meanwhile, the results also indicated that there was a certain extent of electrostatic force and hydrogen bonding, but they maybe play an auxiliary role. The CD measurement results confirmed the alteration in the helical configuration of ct-DNA but almost no change in the base stacking after binding DSTN. The results revealed that there was the obvious change in the conformation, the dipole moment, and the atomic charge distribution of DSTN in the B-DNA complexes, compared with free DSTN, to satisfy the conformational adaptation. From the obtained fronitier molecular orbitals of DSTN, it can be inferred that the nature of DSTN alters with the change of the environment around DSTN. Communicated by Ramaswamy H. Sarma.

Multispectroscopic studies on the interaction of a copper(ii) complex of ibuprofen drug with calf thymus DNA

The interaction of copper(II)-ibuprofenato complex with calf thymus DNA (ct-DNA) has been explored following, UV-visible spectrophotometry, fluorescence measurement, dynamic viscosity measurements, and circular dichroism spectroscopy. In spectrophotometric studies of ct-DNA it was found that [Cu(ibp)₂]₂ can form a complex with double-helical DNA. The association constant of [Cu(ibp)₂]₂ with DNA from UV-Vis study was found to be 6.19 × 10⁴ L mol^-1. The values of K_f from fluorescence measurement clearly underscore the high affinity of [Cu(ibp)₂]₂ to DNA. The experimental results showed that the conformational changes in DNA helix induced by [Cu(ibp)₂]₂ are the reason for the fluorescence quenching of the DNA-Hoechst system. In addition, the fluorescence emission spectra of intercalated methylene blue (MB) with increasing concentrations of [Cu(ibp)₂]₂ represented a significant increase of MB intensity as to release MB from MB-DNA system. The results of circular dichroism (CD) suggested that copper(II)-ibuprofenato complex can change the conformation of DNA. In addition, the results of viscosity measurements suggest that copper(II)-ibuprofenato complex may bind with non-classical intercalative mode. From spectroscopic and hydrodynamic studies, it has been found that [Cu(ibp)₂]₂ interacts with DNA by partial intercalation mode which contains intercalation and groove properties.

Interaction of two new mixed ligand copper(II) complexes with DNA probed by thermodynamic and spectroscopic studies

The DNA binding behavior of [Cu(4,7-dmp)(phen-dione)Cl]Cl (1) and [Cu(2,9-dmp)(phen-dione)Cl]Cl (2) where dmp and phen-dion stand for dimethyl-1,10-phenanthroline and 1,10-phenanthroline-5,6-dion, respectively, was studied with a series of techniques including Viscometry, UV-Vis absorption, circular dichroism and fluorescence spectroscopy. Cytotoxicity effect was also investigated. Thermodynamic parameters, enthalpy and entropy changes were calculated according to Van't Hoff equation, which indicated that both reactions are predominantly enthalpically driven. However, these two complexes show different behavior in fluorescence, circular dichroism and viscometry methods which indicate the Cu(II) complexes interact with calf-thymus DNA by different mode of binding. These have further been verified by competition studies using Hoechst as a distinct groove binder. All these results indicate that these two complexes (1) and (2) interact with CT-DNA via groove binding and partially intercalative mode, respectively and the binding affinity of the complex 1 is higher than that of complex 2. Finally, our findings suggest that the type of ligands and structure of complexes have marked effect on the binding affinity of complexes involving CT-DNA. Also, these new complexes showed excellent antitumor activity against human T lymphocyte carcinoma-Jurkat cell line.

Determining the mode of interaction of calf thymus DNA with the drug sumatriptan using voltammetric and spectroscopic techniques

The interaction of native calf thymus DNA with sumatriptan(1-[3-(2-dimethylaminoethyl)-1H-indol-5-yl]-N-methyl-methanesulfonamide) at physiological pH was studied by spectrophotometry, circular dichroism, voltammetry and viscosimetric techniques. Sumatriptan molecule intercalated between base pairs of DNA, showed by a sharp increase in specific viscosity of DNA. In cyclic voltammetry, decrease of the peak current and positive shift indicated that this drug is able to intercalate between the DNA base pairs. In addition, the drug induced changes in the CD spectrum of CT-DNA, as well as hypochromism changes in its UV-vis spectrum.

DNA-binding studies of fluoxetine antidepressant

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) antidepressant that is widely prescribed. The DNA-binding behavior of fluoxetine antidepressant and calf thymus DNA was investigated in Tris-HCl buffer at physiological pH 7.4 with a series of techniques, including UV-Vis and circular dichroism spectroscopies, competitive study with Hoechst 33258, viscometry, and cyclic voltammetry. Fluoxetine molecules bind to DNA via groove mode as illustrated by hypochromism with no red shift in the UV absorption band of fluoxetine, decrease in Hoechst-DNA solution fluorescence, and no significant changes in viscosity of DNA. The CD spectra of DNA molecules show a little change in stacking mode of base pair but no modification changes in DNA conformation, for example, from B-DNA to A or C-DNA. The binding constant (K(b)) of DNA with fluoxetine was calculated to be 6.7 × 10(4) M(-1), which is in the range of reported and known groove binders, such as distamycin. All results showed the groove-binding mode of interaction of fluoxetine with DNA.

DNA binding, DNA cleavage and cytotoxicity studies of a new water soluble copper(II) complex: the effect of ligand shape on the mode of binding

The interaction of native calf thymus DNA (CT-DNA) with [Cu(ph(2)phen)(phen-dione)Cl]Cl was studied at physiological pH by spectrophotometric, spectrofluorometric, circular dichroism, and viscometric techniques. Considerable hypochromicity and red shift are observed in the UV absorption band of the Cu complex. Binding constants (K(b)) of DNA with the complex were calculated at different temperatures. Thermodynamic parameters, enthalpy and entropy changes were calculated according to Van't Hoff equation, which indicated that reaction is predominantly enthalpically driven. All these results indicate that Cu(II) complex interacts with CT-DNA via intercalative mode. Also, this new complex induced cleavage in pUC18 plasmid DNA as indicated in gel electrophoresis and showed excellent antitumor activity against K562 (human chronic myeloid leukemia) and human T lymphocyte carcinoma-Jurkat cell lines.