Binding Interaction of Coumarin Derivative Daphnetin with Ovalbumin: Molecular Insights into the Complexation Process and Effects of Metal Ions and pH in the Binding and Antifibrillation Studies.

This study investigates the interaction between daphnetin and ovalbumin (OVA) as well as its potential to inhibit OVA fibrillation using both spectroscopic and computational analysis. A moderate binding affinity of 1 × 104 M-1 was observed between OVA and daphnetin, with a static quenched mechanism identified during the fluorescence quenching processes. Metal ions' (Cu2+ and Zn2+) presence led to an increase in the binding affinities of daphnetin toward OVA, mirroring a similar trend observed with the pH variation. Synchronous and 3D fluorescence studies indicated an increase in the polarity of the microenvironment surrounding the Trp residues during binding. Interestingly, circular dichroism and Fourier transform infrared studies showed a significant change in the secondary structure of OVA upon binding with daphnetin. The efficacy of daphnetin in inhibiting protein fibrillation was confirmed through thioflavin T and Congo Red binding assays along with fluorescence microscopic imaging analysis. The thermodynamic assessment showed positive ΔH° [+(29.34 ± 1.526) kJ mol-1] and ΔS° [+(181.726 ± 5.465) J mol-1] values, indicating the presence of the hydrophobic forces, while negative ΔG° signifies spontaneous binding interactions. These experimental findings were further correlated with computational analysis, revealing daphnetin dynamics within the binding site of OVA.

Strategic design and development of a siderophore mimic: pioneering anticancer therapy via ROS generation and ferroptosis.

We designed a tris-catecholate-based siderophore mimic, H6-T-CATL, to selectively chelate iron(III) from mitochondrial cytochromes and other iron-containing proteins within cellular matrices. This strategic sequestration aims to trigger apoptosis or ferroptosis in cancer cells through the glutathione (GSH)-dependent release of reduced iron and subsequent ROS-mediated cytotoxicity. Synthesis of H6-T-CATL involved precise peptide coupling reactions. Using the Fe(III)-porphyrin model (Fe-TPP-Cl), akin to cytochrome c, we studied H6-T-CATL's ability to extract iron(III), yielding a binding constant (Krel) of 1014 for the resulting iron(III) complex (FeIII-T-CATL)3-. This complex readily underwent GSH-mediated reduction to release bioavailable iron(II), which catalyzed Fenton-like reactions generating hydroxyl radicals (˙OH), confirmed by spectroscopic analyses. Our research underscores the potential of H6-T-CATL to induce cancer cell death by depleting iron(III) from cellular metalloproteins, releasing pro-apoptotic iron(II). Evaluation across various cancer types, including normal cells, demonstrated H6-T-CATL's cytotoxicity through ROS production, mitochondrial dysfunction, and activation of ferroptosis and DNA damage pathways. These findings propose a novel mechanism for cancer therapy, leveraging endogenous iron stores within cells. H6-T-CATL emerges as a promising next-generation anticancer agent, exploiting iron metabolism vulnerabilities to induce selective cancer cell death through ferroptosis induction.