Synthesis, characterization and interactions with the oligonucleotide d(5′-CGCGAATTCGCG-3′) 2 , of bis(terpyridine)ruthenium(II)–peptide conjugates

Copper(ii) complexes supported by modified azo-based ligands: Nucleic acid binding and molecular docking studies

Two new copper(ii) complexes [CuL1] (1) and [CuL2] (2) derived from azo-based ligands 2-hydroxy-5-p-tolylazo-benzaldehyde (HL1) and 1-(2-hydroxy-5-p-tolylazo-phenyl)-ethan-one (HL2) were synthesized. These two ligands and their metal complexes were characterized by elemental analysis, nuclear magnetic resonance (1H and 13C), infrared, and UV/Vis spectroscopic techniques. Spectroscopy and other theoretical studies reveal the geometry of copper complexes, and their binding affinity towards nucleic acids are major groove binding.

In vitro investigation of biophysical interactions between Ag(I) complexes of bis(methyl)(thia/selena)salen and ct-DNA via multi-spectroscopic, physicochemical and molecular docking methods along with cytotoxicity study

Four silver(I) (Ag(I)) complexes: 1.PF₆ , 2.PF₆ , 1.ClO₄ and 2.ClO₄ of bis(methyl)thia salen (1) and bis (methyl)selena salen (2) with two different counter anions (PF₆ ^- and ClO₄ ^- ) have been investigated for DNA binding properties. In vitro interactional association between the Ag(I) complexes and ct-DNA has been examined by performing spectroscopic titrations on absorption spectrophotometer and fluorescence spectrophotometer. A competitive binding study has also been done using a fluorescence spectrophotometer with ethidium bromide as a classical intercalator. The spectroscopic methods revealed a major groove. Viscometry and agarose gel electrophoresis experiments have also been performed as physicochemical methods to confirm the binding of complex molecules with DNA. Molecular docking analysis has been executed to obtain the theoretical insight into the mode of binding. The docking study demonstrated the major groove binding of all four complexes to the DNA with electrostatic metal-phosphate interactions (between the metal and the backbone of DNA) and hydrophobic interactions. Cytotoxicity of the complexes has been studied on the Human Fibroblast foreskin (HFF) cell line. The cytotoxicity results showed positive gesture for moving ahead to the next level of screening; the values were above 10 μM which are appreciated for the normal cell lines.

"Chemistry-on-the-complex": functional RuII polypyridyl-type sensitizers as divergent building blocks

Ruthenium polypyridyl type complexes are potent photoactive compounds, and have found - among others - a broad range of important applications in the fields of biomedical diagnosis and phototherapy, energy conversion schemes such as dye-sensitized solar cells (DSSCs) and molecular assemblies for tailored photo-initiated processes. In this regard, the linkage of RuII polypyridyl-type complexes with specific functional moieties is highly desirable to enhance their inherent photophysical properties, e.g., with a targeting function to achieve cell selectivity, or with a dye or redox-active subunits for energy- and electron-transfer. However, the classical approach of performing ligand syntheses first and the formation of Ru complexes in the last steps imposes synthetic limitations with regard to tolerating functional groups or moieties as well as requiring lengthy convergent routes. Alternatively, the diversification of Ru complexes after coordination (termed "chemistry-on-the-complex") provides an elegant complementary approach. In addition to the Click chemistry concept, the rapidly developing synthesis and purification methodologies permit the preparation of Ru conjugates via amidation, alkylation and cross-coupling reactions. In this regard, recent developments in chromatography shifted the limits of purification, e.g., by using new commercialized surface-modified silica gels and automated instrumentation. This review provides detailed insights into applying the "chemistry-on-the-complex" concept, which is believed to stimulate the modular preparation of unpreceded molecular assemblies as well as functional materials based on Ru-based building blocks, including combinatorial approaches.

Stepwise synthesis, characterization, DNA binding properties and cytotoxicity of diruthenium oligopyridine compounds conjugated with peptides

Although the interactions of oligopyridine ruthenium complexes with DNA have been widely studied, the biological activity of similar diruthenium oligopyridine complexes conjugated with peptides has not been investigated. Herein, we report the stepwise synthesis and characterization of diruthenium complexes with the general formula [(L^a)Ru(tppz)Ru(L^b)]ⁿ⁺ (tppz = 2,3,5,6-tetra(2-pyridyl)pyrazine, L^a = 2,2':6',2''-terpyridine or 4-phenyl-2,2':6',2''-terpyridine and L^b = 2,2':6',2''-terpyridine-4'-CO(Gly¹-Gly²-Gly³-LysCONH₂) (5), (6), n = 5; 2,2':6',2''-terpyridine-4'-CO(Gly¹-Gly²-Lys¹-Lys²CONH₂) (7), (8), n = 6; 2,2':6',2''-terpyridine-4'-CO(Ahx-Lys¹Lys²CONH₂) (9), (10), n = 5, Ahx = 6-aminohexanoic acid). The compounds [(trpy)Ru(tppz)Ru(trpy-CO₂H)](PF₆)₄, (2)(PF₆)₄, [(ptrpy)Ru(tppz)Ru(trpy-CO₂H)](PF₆)₄, (3)(PF₆)₄ and [(ptrpy)Ru(tppz)Ru(trpy)](PF₆)₄, (4)(PF₆)₄ were also characterized by single crystal X-ray methods. Moreover, the interactions of the chloride salts (5), (6) and (4) with the self-complementary dodecanucleotide duplex d(5'-CGCGAATTCGCG-3')₂ were studied by NMR spectroscopic techniques. The results show that complex (4) binds in the central part of the oligonucleotide, from the minor groove through the ligand ptrpy, while the ligand trpy, which was located on the other side of the diruthenium core, does not contribute to the binding. Complex (5) binds similarly, through the ligand ptrpy. However, the induced upfield shifts of the ptrpy proton signals are significantly lower than the corresponding ones in the case of (4), indicating much lower binding affinity. This is clear evidence that the tethered peptide Gly¹-Gly²-Gly³-Lys¹CONH₂ hinders the complex binding, even though it contains groups that are able to assist it (e.g., the positively charged amino group of lysine, the peptidic backbone, the terminal amide). Complex (6) shows a non-specific binding, interacting through electrostatic forces. The chloride salts of (4), (5) and (6) had insignificant effects on the cell cycle distribution and marginal cytotoxicity (IC₅₀ > 750 μM) against human lung cancer cell lines H1299 and H1437, indicating that their binding to the oligonucleotide is not a sufficient condition for their cytotoxicity.