ABSTRACT
Organometallic rhodium(III) complexes with curcuminoid ligands attracted considerable attention in biological-related fields and the variation of curcuminoid ligands may regulate the biological activity of these organometallic rhodium(III) complexes. To deeply evaluate the biological influences of these complexes, the binding interactions between three rhodium(III) complexes with curcuminoid ligands and human serum albumin (HSA) were comparably investigated by spectroscopic and electrochemical techniques. The results suggested that the intrinsic fluorescence of HSA was quenched by three complexes through static fluorescence quenching mode. Three complexes bonded with Sudlow's site I of HSA to form ground-state compounds under the binding forces of van der Waals interactions, hydrogen bonds formation, and protonation. Finally, the native conformational structure and the thermal stability of HSA were all changed. Space steric hindrance of complexes took part in the differences of the fluorescence quenching processes, and the chemical polarity of the complexes played a vital role in the variations of the structure and biological activity of HSA. These results illustrated the molecular interactions between protein and organometallic rhodium(III) complexes with curcuminoid ligands, offering new insight about the prospective applications of analogical rhodium(III) complexes in biomedicine areas.
Subject(s)
Diarylheptanoids/metabolism , Organometallic Compounds/chemistry , Rhodium/chemistry , Serum Albumin, Human/metabolism , Binding Sites , Circular Dichroism , Diarylheptanoids/chemistry , Humans , Hydrogen Bonding , Ligands , Models, Molecular , Protein Binding , Protein Conformation , Serum Albumin, Human/chemistry , ThermodynamicsABSTRACT
Rhodium(III) complexes such as [Rh(Chi4Hy3mb)(H2O)2]Cl2, [Rh(Chi2Hymb)(H2O)2]Cl2, and [Rh(Chi2Hy3mb)(H2O)2]Cl2 were synthesized by metal chelation/complexation with chitosan Schiff base ligands. Stable Schiff base ligands were prepared by chemical modification of chitosan with aromatic aldehydes such as vanillin, salicylaldehyde and orthovanillin. These chitosan based Schiff base ligands were performed as bidentate ligands through azomethine nitrogen atom and methoxy/hydroxy oxygen atom. These bidentate ligands were favoured to the formation of stable coordination complex with metal ions. The series of Rhodium(III) complexes were characterized by Elemental analysis, FT-IR, UV-Vis spectroscopy, P-XRD and Thermo-gravimetric analysis (TGA). The electrochemical property of Rhodium(III) complexes were analyzed by cyclic voltametry.
Subject(s)
Coordination Complexes/chemical synthesis , Electrochemical Techniques , Temperature , Azo Compounds/chemistry , Biopolymers/chemistry , Chitosan/chemistry , Coordination Complexes/chemistry , Ligands , Molecular Structure , Rhodium/chemistry , Schiff Bases/chemistry , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform Infrared , Thiosemicarbazones/chemistry , X-Ray DiffractionABSTRACT
A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl3] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 104. In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV-Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters (ΔH, ΔS, and ΔG) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Benzimidazoles/chemistry , DNA/metabolism , Organometallic Compounds/chemical synthesis , Organometallic Compounds/pharmacology , Pyridines/chemistry , Rhodium/chemistry , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/metabolism , Cattle , Cell Line, Tumor , Chemistry Techniques, Synthetic , DNA/chemistry , Models, Molecular , Nucleic Acid Conformation , Organometallic Compounds/chemistry , Organometallic Compounds/metabolism , Protein Binding , Serum Albumin, Bovine/metabolism , ThermodynamicsABSTRACT
The cation of the title compound, [Rh(η(5)-C5Me5)Cl(C13H12ClN3)]Cl, adopts a typical piano-stool geometry. The complex is chiral at the metal and crystallizes as a racemate. Upon coordination, the hydrazinyl-idene-pyridine ligand is non-planar, an angle of 54.42â (7)° being observed between the pyridine ring and the aromatic ring of the [2-(4-chloro-phen-yl)hydrazin-1-yl-idene]ethyl group. In the crystal, a weak inter-ionic N-Hâ¯Cl hydrogen bond is observed.