RESUMEN
Telomerase inhibition through G-quadruplex stabilization by small molecules is of great interest as a novel anticancer therapeutic strategy. Here, we show that newly synthesized Cu-complex binds to G-quadruplex DNA and induces changes in its stability. This biophysical interaction was investigated in vitro using spectroscopic, voltammetric and computational techniques. The binding constant for this complex to G-quadruplex using spectroscopic and electrochemical methods is in the order of 10(5) . The binding stoichiometry was investigated using spectroscopic techniques and corresponded to a ratio of 1: 1. Fluorescence titration results reveal that Cu-complex is quenched in the presence of G-quadruplex DNA. Analysis of the fluorescence emission at different temperatures shows that ΔH° > 0, ΔS° > 0 and ΔG° < 0, and indicates that hydrophobic interactions played a major role in the binding processes. MD simulation results suggested that this ligand could stabilize the G-quadruplex structure. An optimized docked model of the G-quadruplex-ligand mixture confirmed the experimental results. Based on the results, we conclude that Cu-complex as an anticancer candidate can bind and stabilize the G-quadruplex DNA structure.
Asunto(s)
Cobre/química , Fluorescencia , G-Cuádruplex , Simulación de Dinámica Molecular , Compuestos Organometálicos/química , Sitios de Unión , Fenómenos Biofísicos , Mediciones Luminiscentes , TermodinámicaRESUMEN
The objective of the present research is to study the interaction of separate and simultaneous of alprazolam (ALP) and fluoxetine hydrochloride (FLX) with human serum albumin (HSA) in phosphate buffer (pH 7.4) using different kinds of spectroscopic, cyclic voltammetry and molecular modeling techniques. The absorbance spectra of protein, drugs and protein-drug showed complex formation between the drugs and HSA. Fluorescence analysis demonstrated that ALP and FLX could quench the fluorescence spectrum of HSA and demonstrated the conformational change of HSA in the presence of both drugs. Also, fluorescence quenching mechanism of HSA-drug complexes both separately and simultaneously was suggested as static quenching. The analysis of UV absorption data and the fluorescence quenching of HSA in the binary and ternary systems showed that FLX decreased the binding affinity between ALP and HSA. On the contrary, ALP increased the binding affinity of FLX and HSA. The results of synchronous fluorescence and three-dimensional fluorescence spectra indicated that the binding of drugs to HSA would modify the microenvironment around the Trp and Tyr residues and the conformation of HSA. The distances between Trp residue and the binding sites of the drugs were estimated according to the Förster theory, and it was demonstrated that non-radiative energy transfer from HSA to the drugs occurred with a high probability. Moreover, according to CV measurements, the decrease of peak current in the cyclic voltammogram of the both drugs in the presence of HSA revealed that they interacted with albumin and binding constants were calculated for binary systems which were in agreement with the binding constants obtained from UV absorption and fluorescence spectroscopy. The prediction of the best binding sites of ALP and FLX in binary and ternary systems in molecular modeling approach was done using of Gibbs free energy.
Asunto(s)
Alprazolam/química , Fluoxetina/química , Modelos Químicos , Modelos Moleculares , Albúmina Sérica/química , Humanos , Unión Proteica , Espectrofotometría UltravioletaRESUMEN
Blocking the division of tumor cells by small-molecules is currently of great interest for the design of new antitumor drugs. The interaction of a new metal complex with DNA was investigated through several techniques. Absorption spectroscopy and gel electrophoresis studies on the interaction of the Cu-complex of (2a-4mpyH)2 [Cu(pyzdc)2 (H2O)2].6 H2O with DNA have shown that this complex can bind to CT-DNA with binding constant 3.99 × 10(5) M(-1). The cyclic voltammetry (CV) responses of the metal complex in the presence of CT-DNA have shown that the metal complex can bind to CT-DNA through partial intercalation mode and this is consistent with molecular docking analysis, quenching process and thermal denaturation experiments. The cytotoxicity of this complex has been evaluated by MTT assay. The results of cell viability assay on DU145 cell line revealed that the metal complex had cytotoxic effects.