Abstract
A new Pt(II) complex, [Pt(DIP)(LL)](NO3)2 (in which DIP is 4,7-diphenyl-1,10-phenanthroline and LL is the aliphatic dinitrogen ligand, N,N-dimethyl-trimethylenediamine), was synthesized and characterized using different physico-chemical methods. The interaction of this complex with calf thymus DNA (CT-DNA) was investigated by absorption, emission, circular dichroism (CD), and viscosity measurements. The complex binds to CT-DNA in an intercalative mode. The calculated binding constant, Kb, was 6.6 × 104 M−1. The enthalpy and entropy changes of the reaction between the complex and CT-DNA showed that the van der Waals interactions and hydrogen bonds are the main forces in the interaction with CT-DNA. In addition, CD study showed that phenanthroline ligand insert between the base pair stack of double helical structure of DNA. It is remarkable that this complex has the ability to cleave the supercoiled plasmid.
Highlights
Cisplatin is one of the most potent antitumor drugs available for the therapeutic management of solid tumors, such as germ cell tumors, ovarian, lung, head and neck, and bladder cancers, and so forth
Materials. 4,7-diphenyl-1,10-phenanthroline (DIP), N, N-dimethyltrimethylenediamine, hydrazine dihydrochloride, potassium Chloride, nitric acid, Tris-acetate-EDTA (TAE) buffer, hydrogen peroxide, NaN3, and Tris-HCl were purchased from Merck
A solution of calf thymus DNA gave a ratio of UV absorbance at 260 and 280 nm more than 1.8, indicating that DNA was sufficiently free from protein
Summary
Cisplatin is one of the most potent antitumor drugs available for the therapeutic management of solid tumors, such as germ cell tumors, ovarian, lung, head and neck, and bladder cancers, and so forth. Many efforts have been directed toward the design of complexes containing modified bipy or phen ligands that bind DNA primarily via base-pair intercalation [9] The examples of this category of DNAbinding agents are metal complexes with polypyridines or 1,10-phenanthrolines (phen) and their derivatives such as 4,7-diphenyl-1,10-phen (DIP) and dipyrido [3,2-a; 29,39c]phenazine (dppz) [7]. To design improved drugs that target DNA and to investigate the effect of mixed-ligand complexes on the structure and conformation of DNA, we used a Pt(II) complex, [Pt(DIP)(LL)](NO3) (in which DIP is 4,7-diphenyl1,10-phenanthroline and LL is the aliphatic dinitrogen ligand, N,N-dimethyl-trimethylenediamine). Binding studies of this complex with calf thymus DNA (CT-DNA) were studied by electronic absorption spectroscopy, fluorescence spectroscopy, circular dichroic spectral, viscosity measurements, and electrophoresis
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