Synthesis, Characterization and Crystal Structure of a New Schiff Base Ligand from a Bis(Thiazoline) Template and Hydrolytic Cleavage of the Imine Bond Induced by a Co(II) Cation

The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H2L (1). Characterization of the ligand was performed by FT-IR, 1H NMR, 13C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO3)2·6H2O and CuCl2·2H2O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.

Metal compound-mediated hydrolytic cleavage of oxidized insulin B chain:Regioselectivity and influence of peptide secondary structure

The interaction of oxidized insulin B chain (B) with cis-[Pd(en)Cl2] (en=ethylenediamine), cis-[Pd-(dtco-3-OH)Cl2] (dtco-3-OH= dithiacyclooctan-3-ol) and CuCl2 was studied by electrospray mass spectrometry. It is discovered that the binding of Pd(II) complexes and the sites of cleavage are highly dependent on the secondary structure and local environment of B. The hydrolytic cleavage of denatured B by Pd(II) complexes was monitored by HPLC. The reaction is regioselective and follows first order kinetics with half-life of 4.8 days at 40oC. Two amide bonds, i. e. at Leu6-Cys7 and at Gly8-Ser9, which are dose to the two potential Pd(II) binding sites His5 and His10, are selectively cleaved. In the case of Cu(II) ion as promoter, only one cleavage site was observed which is located at Gly8-Ser9 bond. These results provide improved understanding on the design of artificial metallopeptidase.

Site-specifically cleavage of oxidized insulin B chain with Zn(Ⅱ) ion studied by electrospray ionization mass spectrometry

The electrospray ionization mass spectrometry and tandem mass spectrometry investigation showed that the binding sites of Zn^2＋ with oxidized insulin B chain are His 5, His 10, and Arg 22, which lead to the selective cleavages of the peptide bonds at Ash 3- Gin 4, His 5-Leu 6, Gly 8-Ser 9, and Glu 21-Arg 22 of oxidized insulin B chain.

Mass spectrometry assisted assignments of binding and cleavage sites of Zn(Ⅱ)complex towards oxidized insulin B chain

The electrospray ionization mass spectrometry investigation showed that the binding sites of [ZnL]^2＋, where L is 2-[bis（2- aminoethyl）amino]ethanol, with oxidized insulin B chain are Phel, His5 and Arg22, which lead to the selective cleavages of the peptide bonds at Phe1-Val2, His5-Leu6, Glu21-Arg22, and Arg22-Gly23 of oxidized insulin B chain.

DNA Cleavage of the Copper(II) Complexes with a Polyamine Ditopic Ligand

A new binuclear complex [Cu2L(OH)](ClO4)3·2H2O has been synthesized and characterized, where L=2,6-bis{[bis-(2-aminoethyl)amino]methyl}-benzene. In the presence of 0.5 mmol/L complex at pH 8.10 and 37°C, the complex can efficiently cleavage pBR322 DNA with a rate constant kobs of 1.35×10-4 s-1. The cleavage occurred by a non-oxidative mechanism showing activity to be dependent on pH.

DNA Cleavage by Copper (Ⅱ) Complexes Without added Coreactants

The cleavage activity of complexes between copper (Ⅱ) and four different amino acidor amino acid methyl ester on DNA was tested at physioloical pH and temperature., It was found that Cu (Ⅱ)-L-His and Cu (Ⅱ)-L-His methyl ester complexes could cleane DNA. The extent ofDNA cleavage is largely dependent on the metal ion-to-ligand ratio. The cleavage of doublestranded DNA mediated by Cu (Ⅱ)-L-His complexes occurs via a hydrolytie mechanism.

DNA-Binding and Cleavage Studies of Zinc（Ⅱ） Mixed-polypyridyl Complex

The complex of Zn[（phen）（dione）Cl]ClO4·H2O （where phen is 1,10-phenanthroline and dione is 1,10-phenanthroline-5,6-dione） has been synthesized and characterized. The interaction of the complex with DNA was investigated using UV absorption, fluorescence spectroscopy, and electrophoresis measurements. The results show that the complex mainly binds to the double helix of DNA with intercalation mode and the binding constant K is 2.4× 10^4 mol^-1·L. Moreover, the complex can efficiently cleave plasmid DNA at physiological pH and temperature. The cleavage occurs via a hydrolysis mechanism, which is showed by adding radical scavengers, rigorously anaerobic experiments, analysis for malondialdehyde-like products, and the hydrolysis experiment of BDNPP with a rate constant kobs of 5.3 × 10^- 6 s^- 1.

Studies of copper (Ⅱ) complexes as catalysts for the hydrolysis of DNA

Hydrolysis of DNA is an important enzymatic reaction , but it is exceedingly difficult to mimic in the laboratory because of the stability of hydrolysis of DNA. In this paper, the cleavage activity of complexes formed between Cu(Ⅱ) and four different amino acid or amino acid methyl ester on DNA is studied by gel elec-trophoresis. It is found that DNA could be cleaved by Cu(Ⅱ)-L-His and Cu(Ⅱ)-L-His methyl ester complexes and the efficiency of cleavage is largely dependent on the metal ion-to-ligand ratio. Further experiments show that the cleavage of DNA mediated by Cu(Ⅱ)-L-His complexes occurs via a hydrolytic mechanism and the active chemical species that affects DNA cleavage is proposed to be MI2H+ and ML2H22+.