Chromophore appended DPA-based copper(II) complexes with a diimine motif towards DNA binding and fragmentation studies

Mixed ligand copper(II) complexes [Cu(L1)(bpy)](ClO4)21 and [Cu(L2)(bpy)](ClO4)22 (where L1 = 1-(anthracen-9-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine, L2 = 1-(pyren-1-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine and bpy = 2,2'-bipyridine) were synthesised and characterised thoroughly via different analytical and spectroscopic techniques i.e., UV-vis spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, HRMS and EPR spectroscopy. The molecular structures of the synthesised complexes were obtained using the single-crystal X-ray diffraction technique. Both complexes exhibited penta-coordinated and acquired distorted square pyramidal geometry. The redox behaviour of complexes 1 and 2 was investigated by employing cyclic voltammetry. The DNA binding study was carried out by UV-vis spectrophotometry using double-stranded salmon sperm DNA (ds-ss-DNA). The binding constant (Kb) values of 1 and 2 were 0.11 × 104 M-1 and 1.05 × 104 M-1, respectively, which indicates that 2 has better binding ability than 1. This might be due to the higher conjugative abilities with the extended surface area of the aromatic pyrene ring compared to the anthracene moiety. The fluorescence quenching experiments were also performed with EB bound DNA (EB-DNA) and Stern-Volmer constant (KSV) values were calculated as 1.23 × 105 M-1 and 1.39 × 105 M-1 for 1 and 2, respectively, suggesting that 2 showed stronger interaction with ss-DNA than 1. The molecular docking data support the DNA-binding studies, with the sites and mode of interactions against B-DNA varying with 1 and 2. Evaluation of the DNA binding properties of the complexes to linearized plasmid DNA indicated that 2 had modest DNA binding properties, which is a pre-requisite for a genotoxic agent. The effect of 1 and 2 on cell survival was analysed using HeLa cells by MTT assay and it was observed that the IC50 values of 1 and 2 were 43.7 μM and 18.6 μM, respectively. Our study paves the way for the designing of bio-inspired novel mixed metal complexes, which shows promising results for further exploration of molecular and mechanistic studies towards the development of non-platinum based economical metallodrugs.

Flow microdialysis sampling-chemiluminescent detection coupled with molecular docking for the investigation of binding behavior between salbutamol and DNA

The investigation of the binding behavior between drug and DNA provides basic information for understanding pharmacological and toxicologic mechanisms of many drugs. Herein, a facile chemiluminescent (CL) method for investigating the binding behavior between salbutamol and calf thymus DNA (ct-DNA) was established by utilizing flow microdialysis sampling technique. In a reaction equilibrium solution of salbutamol and ct-DNA, free salbutamol was extracted by a microdialysis probe, and then injected into a flow-injection CL detection system to quantitate its concentration. The binding constants of salbutamol acquired by Klotz analysis and Scatchard analysis were 2.97 × 10⁴ M^-1and 2.99 × 10⁴ M^-1, respectively. Salbutamol showed one sort of binding site on ct-DNA. Meanwhile, the three-dimensional spatial structure of the binding mode was investigated by molecular docking. The results indicate that the binding mode of salbutamol to ct-DNA was groove binding. The hydrogen bonds were primary driving force for the direct recognition of salbutamol by ct-DNA. This proof-of-principle method paves a pathway to investigate the binding behavior between small-molecular drug and DNA, and provides a theoretical guidance for designing DNA-targeting drugs.

Design, antiviral and cytostatic properties of isoxazolidine-containing amonafide analogues

A novel series of 5-arylcarbamoyl- and 5-arylmethyl-2-methylisoxazolidin-3-yl-3-phosphonates have been synthesized via cycloaddition of N-methyl-C-(diethoxyphosphoryl)nitrone with N-substituted naphthalimide acrylamides and N-allylnaphthalimides. All cis- and trans-isoxazolidine phosphonates obtained herein were assessed for antiviral activity against a broad range of DNA and RNA viruses. Isoxazolidines trans-9d and trans-9f exhibited the highest activity (EC₅₀ = 8.9 μM) toward cytomegalovirus. Compounds cis- and trans-9d as well as cis- and trans-9f were found potent against HSV and Vaccinia viruses (EC₅₀ in the 45–58 μM range), whereas isoxazolidines 10a and 10d suppressed replication of Coxsackie B4 and Punta Toro viruses (EC₅₀ in the 45–73 μM range). Antiproliferative evaluation of all obtained isoxazolidines revealed the promising activity of cis-9b, cis-9d, trans-9d, cis-9e, trans-9e, cis-9f and trans-9f toward tested cancer cell lines with IC₅₀ in the 1.1–19 μM range.

An α1-adrenergic receptor ligand repurposed as a potent antiproliferative agent for head and neck squamous cell carcinoma

In this study we report the anticancer properties of RN5-Me, an α₁-adrenergic receptor ligand.

#Nitrosocarbonyls 1: antiviral activity of N-(4-hydroxycyclohex-2-en-1-yl)quinoline-2-carboxamide against the influenza A virus H1N1

Influenza virus flu A H1N1 still remains a target for its inhibition with small molecules. Fleeting nitrosocarbonyl intermediates are at work in a short-cut synthesis of carbocyclic nucleoside analogues. The strategy of the synthetic approaches is presented along with the in vitro antiviral tests. The nucleoside derivatives were tested for their inhibitory activity against a variety of viruses. Promising antiviral activities were found for specific compounds in the case of flu A H1N1.

Recent advances in small organic molecules as DNA intercalating agents: synthesis, activity, and modeling

The interaction of small molecules with DNA plays an essential role in many biological processes. As DNA is often the target for majority of anticancer and antibiotic drugs, study about the interaction of drug and DNA has a key role in pharmacology. Moreover, understanding the interactions of small molecules with DNA is of prime significance in the rational design of more powerful and selective anticancer agents. Two of the most important and promising targets in cancer chemotherapy include DNA alkylating agents and DNA intercalators. For these last the DNA recognition is a critical step in their anti-tumor action and the intercalation is not only one kind of the interactions in DNA recognition but also a pivotal step of several clinically used anti-tumor drugs such as anthracyclines, acridines and anthraquinones. To push clinical cancer therapy, the discovery of new DNA intercalators has been considered a practical approach and a number of intercalators have been recently reported. The intercalative binding properties of such molecules can also be harnessed as diagnostic probes for DNA structure in addition to DNA-directed therapeutics. Moreover, the problem of intercalation site formation in the undistorted B-DNA of different length and sequence is matter of tremendous importance in molecular modeling studies and, nowadays, three models of DNA intercalation targets have been proposed that account for the binding features of intercalators. Finally, despite DNA being an important target for several drugs, most of the docking programs are validated only for proteins and their ligands. Therefore, a default protocol to identify DNA binding modes which uses a modified canonical DNA as receptor is needed.

New PAH derivatives functionalized by cyclic nitrone framework: synthetic design, anti-proliferative activity and interaction with DNA

Novel approach to functionalized polycyclic aromatic hydrocarbons (PAHs) is presented. Incorporation of cyclic nitrone framework into the structure of PAHs was studied with respect to their anti-proliferative activities and interaction with double stranded DNA. Theoretical docking studies and UV titration methods were used for preliminary evaluation of binding of new PAH derivatives to DNA structure.

Effects of the biological backbone on DNA-protein stacking interactions

The pi-pi stacking (face-to-face) interactions between the five natural DNA or RNA nucleobases and the four aromatic amino acids were compared using three different types of dimers: (1) a truncated nucleoside (nucleobase) stacked with a truncated amino acid; (2) a truncated nucleoside (nucleobase) stacked with an extended amino acid; and (3) a nucleoside (extended nucleobase) stacked with a truncated amino acid. Systematic (MP2/6-31G*(0.25)) potential energy surface scans reveal important information about the effects of the deoxyribose sugar and protein backbone on the structure and binding energy between truncated nucleobase and amino acid models that are typically implemented in the literature. Most notably, electrostatic and steric interactions arising from the bulkiness of the biological backbones can change the preferred relative orientations of DNA and protein pi-systems. More importantly, the protein backbone can strengthen the stacking energy (by up to 10 kJ mol(-1)), while the deoxyribose moiety can strengthen or weaken the stacking interaction depending on the positioning of the amino acid relative to the sugar residue. These effects are likely due to additional interactions between the amino acid or nucleobase ring and the backbone in the extended monomer rather than significant changes in the properties of the biological pi-systems upon model extension. Since the present work reveals that all calculated DNA-protein stacking interactions are significant and approach the strength of other noncovalent interactions between biomolecules, both pi-pi and backbone-pi interactions must be considered when attempting to gain a complete picture of DNA-protein binding.