DNA-binding and cleavage studies of novel copper(II) complex with l-phenylalaninate and 1,4,8,9-tetra-aza-triphenylene ligands

DNA-binding properties of novel copper(II) complex [Cu(l-Phe)(TATP)(H(2)O)](+), where L-Phe=L-phenylalaninate and TATP=1,4,8,9-tetra-aza-triphenylene are investigated using electronic absorption spectroscopy, fluorescence spectroscopy, voltammetry and viscosity measurement. It is found that the presence of calf thymus DNA results in a hypochromism and red shift in the electronic absorption, a quenching effect on fluorescence nature of ethidium bromide-DNA system, an enhanced response on voltammograms of [Co(phen)(3)](3+/2+)-DNA system, and an obvious change in viscosity of DNA. From absorption titration, fluorescence analysis and voltammetric measurement, the binding constant of the complex with DNA is calculated. The latter two methods reveal the stronger binding of [Cu(l-Phe)(TATP)(H(2)O)](+) complex to double strand DNA by the moderate intercalation than [Co(phen)(3)](3+). Such a binding induces the cleavage of plasmid pBR322 DNA in the presence of H(2)O(2).

“Naked-Eye” Detection of Histidine by Regulation of CuII Coordination Modes

The association of various alpha-amino acids with four new, coordinatively unsaturated metal complexes ([Cu(5)]2+, [Cu(6)]2+, [Cu(7)]2+, and [Zn(8)]2+) was examined. The receptors [Cu(5)]2+ and [Cu(7)]2+ were found to discriminate histidine (His) from other zwitterionic alpha-amino acids by means of indicator-displacement assays (IDAs) using 5(6)-carboxyfluorescein as an indicator in buffered methanol/water (3:1) solvent. The colorimetric detection of His was achieved by using this IDA method, which appears to owe its selectivity to a unique process involving disruption of the host complex to form a 2:1 His/Cu(II) complex rather than simple indicator displacement. The occurrence of distinct intermolecular coordination processes in response to the introduction of a different amino acid is observed. X-ray crystal structures of the host metal complexes were obtained and exhibit the adoption of a variety of coordination geometries about the metal center.