RESUMO
G-quadruplexes play a pivotal role in regulating various cellular processes, including gene expression and replication, making them essential structures in understanding, and manipulating cellular functions. The development of G-quadruplex ligands holds significant promise in therapeutic and research applications, offering targeted tools to modulate G-quadruplex structures and potentially influence critical biological pathways. An exciting frontier in G-quadruplex research lies in the exploration of anionic ligands, and their profound impact on stabilizing and modulating G-quadruplex DNA. In this study, the interaction of two anionic phthalocyanine compounds (Zinc (II) phthalocyanine 3,4',4â³,4â´-tetrasulfonic acid, tetrasodium salt, ZnAPC; cobalt (II) phthalocyanine 3,4',4â³,4â´-tetrasulfonic acid, tetrasodium salt, CoAPC) and three separate G-quadruplex-forming DNA sequences was investigated. Interactions were carried out by DNA polymerase stop studies along with spectroscopic studies. According to the results of experimental data, it was determined that ZnAPC actively interacts with the G-quadruplex DNA structures. On the other hand, it was thought that the interaction with CoAPC was less and even occurred in simple electrostatic interactions. KD constants and Bmax constants for the interaction with ZnAPC were calculated. The KD constants for ZnAPC were found to be (1.16 ± 0.07) × 10-5, (9.75 ± .24) × 10-6 and (1.00 ± 0.36) × 10-4 M for AS1411, Vegf, and Tel21, respectively. Accordingly, it was concluded that ZnAPC interacts with G-quadruplex DNA ligands effectively.
Assuntos
Quadruplex G , DNA/química , Isoindóis , Zinco/química , LigantesRESUMO
G-quadruplexes are important drug targets and get attention due to their existence in telomere, ribosomal DNA, promoter regions of some oncogenes, and the untranslated regions of mRNA. Due to the biological roles of G-quadruplexes, investigating of the G-quadruplex-small molecule interaction is essential. The primary motivation for these studies is the possibility of inhibiting cell functions associated with G-quadruplex sequences by binding with small molecules. Targeting the small molecules to desired tissue with the G-quadruplex vehicles is the second important goal of the G-quadruplex-small molecule interaction studies. In the present study, the new peripherally 2-mercaptopyridine octasubstituted copper(II) phthalocyanine and its quaternized derivative (CuPc) were synthesized and characterized by elemental analysis FT-IR, UV-Vis, and mass spectra. The excellent solubility of CuPc in water is essential for its transport in the organism. Because of this feature, its affinity toward G-quadruplex forming aptamers, AS1411, Tel21, and Tel45, was investigated. The UV-Vis spectrophotometric titration data confirmed the prevention of aggregation upon interaction with G-quadruplex, which is very important for biomedical applications. The CD spectroscopic analyses and binding stoichiometry confirmed the "end stacking" model for interaction of AS1411 with CuPc. The interaction of CuPc caused the equilibrium shift from hybrid conformation to antiparallel conformation for Tel21 and Tel45. The isothermal titration calorimeter (ITC) was used for the determination of thermodynamic parameters. The thermodynamic data of the interaction was fitted well with the one-site model. The negative values of Gibbs free energy change confirmed the spontaneous nature of the reactions. Besides, the negative values of enthalpy change and entropy change proved that the nature of processes was "enthalpy driven." The interaction stoichiometry was 2 for AS1411 and Tel21 and 1.5 for Tel45. The binding constants were 1.3(±0.3) × 105 , 3.2(±0.4) × 105 , and 1.1(±0.3) × 105 M-1 , which were at the level of ethidium bromide intercalation binding constant given in the literature. The DNA polymerase stop assay further supported the interaction of CuPc with G-quadruplex DNA. The experimental results confirm that the CuPc has a potential photosensitizer behaviour for photodynamic therapy.