Acceleration of Hydrolytic DNA Cleavage by Dicopper(II) Complexes withp-Cresol-Derived Dinucleating Ligands at Slightly Acidic pH and Mechanistic Insights

Abstract

Four dicopper(II) complexes, [Cu2(µ-X)(bcmp)](ClO4)2 [X = OH (1a) and X = Cl (1b)], [Cu2(µ-OH)(Me4bcmp)](ClO4)2 (2), and [Cu2(bcc)](ClO4)3 (3), were synthesized with three p-cresol-derived ligands, 2,6-bis(1,4,7-triazacyclononylmethyl)-4-meth-ylphenol (Hbcmp), 2,6-bis(1,4,7-triaza-4,7-dimethylcyclonon-ylmethyl)-4-methylphenol (HMe4bcmp), and 2,6-bis(1,4,7,10-tetrazacyclododecylmethyl)-4-methylphenol (Hbcc) to study hydrolytic DNA cleavage. Crystal structures of 1a, 1b, 2, and 3 were determined by X-ray analysis. The pH titrations and spectroscopic studies in the complexations of the ligands with copper(II) perchlorate revealed that the dicopper core structures of 1a, 2, and 3 in the solid state are kept at pH 5–9 in an aqueous solution. DNA binding abilities of 1a, 2, and 3 were examined by isothermal titration calorimetry (ITC). DNA cleavage studies were carried out by using supercoiled plasmid pUC19 DNA. 1a largely accelerated hydrolytic DNA cleavage at pH 5–6 but not at pH 7–8. This is the first example of pH-dependent DNA cleavage by a dicopper complex. Inhibition studies with specific DNA binders, 4′,6-diamidino-2-phenylindole and methyl green, suggested that 1a accelerates the DNA cleavage via GC-specific binding. The mechanistic insights into the pH-dependent DNA cleavage are proposed on the basis of the crystal structures, structures in aqueous solutions, DNA binding modes, and DNA cleavage activities of 1a, 1b, 2, and 3.

Oxidative DNA Cleavage, Formation of μ-1,1-Hydroperoxo Species, and Cytotoxicity of Dicopper(II) Complex Supported by a p-Cresol-Derived Amide-Tether Ligand

“…Previously, we reported that a dicopper­(II) complex with p -cresol-derived methylene-tether ligand [Cu 2 (bcc)]­(ClO 4 ) 3 ( 1 ) and related complexes accelerate hydrolytic DNA cleavage at pH 5–6, but 1 did not accelerate the DNA cleavage with H 2 O 2 . In this study, we synthesized a new p -cresol-derived amide-tether ligand 2,6-bis­(1,4,7,10-tetraazacyclododecyl-1-carboxamide)- p -cresol (Hbcamide) and found that its dicopper­(II) complex [Cu 2 (μ-OH)­(bcamide)]­(ClO 4 ) 2 ( 2 ) largely accelerates the oxidative DNA cleavage by H 2 O 2 without reductants.…”

“…The methylene- and amide-tether ligands, Hbcc and Hbcamide, used in this study have two tetraazacyclododecane (cyclen) pendant groups tethered at 2,6-positions of p -cresol by −CH 2 – and −CO– groups, respectively (Scheme ). Hbcc and [Cu 2 (bcc)]­(ClO 4 ) 2 ( 1 ) were prepared as previously reported . Hbcamide and [Cu 2 (μ-OH)­(bcamide)]­(ClO 4 ) 2 ( 2 ) are new compounds, and the synthetic details are shown in the Supporting Information.…”

Dicopper(II) Complexes of p-Cresol-2,6-Bis(dpa) Amide-Tether Ligands: Large Enhancement of Oxidative DNA Cleavage, Cytotoxicity, and Mechanistic Insight by Intracellular Visualization

“…The synthetic details and spectroscopic characterization of HL1, HL2, 1 , 2a , b , and 3 are given in the Experimental Section. HL3, HL4, 4 , and 5 were prepared according to the literature. , HL1 was prepared in almost quantitative yield from bis­(2-pyridylmethyl)­amine and 4-methylphenol-2,6-dicarboxylic acid via formation of acid chloride by treatment with thionyl chloride. In this reaction, potassium carbonate was used as the base, but the yield of HL1 drastically decreased when triethylamine was used as the base.…”

“…All ordinary reagents including N,N′ -dicyclohexylcarbodiimide (DCC), 4-dimethylaminopyridine (DMAP), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), trifluoroacetic acid (TFA), N -(3-(dimethylamino)­propyl)- N′ -ethylcarbodiimide hydrochloride (EDC·HCl), and solvents were purchased and used as received unless otherwise noted. The dicopper complexes of HL3 and HL4, [Cu 2 (μ-OH)­(L3)]­(ClO 4 ) 2 ( 4 ) and [Cu 2 (μ-OH)­(L4)]­(ClO 4 ) 2 ( 5 ) respectively, were synthesized according to the literature. , pUC19 DNA was purchased from Nippon Gene Co., Ltd. 4-Methylphenol-2,6-dicarboxylic acid ( 6 ), 1-amino-8-azido-3,6-dioxaoctane ( 12 ), and complex 5 were prepared according to the literature. ,, Caution! Perchlorate salts are potentially explosive and should be handled with great caution .…”

“…N-(8-Azido-3,6-dioxaoctyl)-2,6-diformyl-1-hydroxy-4-benzamide (13). 11 (4.19 g, 21.6 mmol), 12 (16.7 g, 71.4 mmol), EDC•HCl (13.7 g, 71.5 mmol), and Et 3 N (10.0 mL, 71.7 mmol) were dissolved in CHCl 3 (400 mL) and stirred at 0 °C under an N 2 atmosphere overnight.…”