title: Synthesis, characterization, DFT studies and DNA binding of mixed platinum (II) complexes containing quinoxaline and 1,2-dithiolate ligands.
abstract: The complexes Pt(pq)Cl2(1) and Pt(pq)(bdt) (2) (where pq = 2-(2'pyridyl)quinoxaline and bdt=benzene-1,2-dithiolate) have been synthesized and fully characterized by UV-visible (UV-Vis), Fourier Transformer Infrared Spectra (FTIR), 1 and 2D NMR and cyclic voltammetry (CV). Interactions of the tested systems (the aforementioned complexes 1 and 2) and the free ligands pq and bdt with double stranded calf thymus DNA (CT-DNA) were studied by UV-spectrophotometric (melting curves) and circular dichroism (CD) measurements. The results suggest that both complexes 1 and 2, are able to form adducts with DNA and to distort the double helix by changing the base stacking. Complex 2 forms stronger adducts to CT-DNA than complex 1 and this is probably due to the substitution of the chlorine atoms of 1 by the 1,2-dithiolate ligand (bdt) in 2. The latter induces an extensive distortion in the planarity of 2 as density functional theory (DFT) calculations reveal. Besides, the light absorbing complex 2 possess intense mixed metal ligand to ligand charge transfer (MM'LLCT) transition in the visible region of the spectrum and could act as photoluminescent metal-based probe for the study of DNA binding. Thus, the photocleavage of DNA by 2 has been studied by UV-Vis and CD spectra and monitored by agarose gel electrophoresis. Under our experimental conditions, it is unclear that complex 2 can photocleave DNA. Furthermore, the ability of 2 to inhibit proliferation of human tumor cell lines was tested and the results indicate some cytoxytic effect on the SF-286 cells.
authors: Laboratory of Inorganic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis Zografou, 157 71 Athens, Greece. cmitsop@chem.uoa.gr
authors: Christiana A
authors: CA
authors: Mitsopoulou
authors: Constantinos E
authors: CE
authors: Dagas
authors: Christodoulos
authors: C
authors: Makedonas
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004563:Electrochemistry; D004587:Electrophoresis, Agar Gel; D006801:Humans; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D009691:Nucleic Acid Denaturation; D009944:Organoplatinum Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011810:Quinoxalines / Q000138:chemical synthesis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D011810:Quinoxalines; D013438:Sulfhydryl Compounds; D004247:DNA