Two copper(II) complexes with tetradentate 1,4-disubstituted-1,2,3-triazole ligands, [CuL(MeCN)](ClO4)2 (1) and [CuL′](ClO4)2 (2), have been prepared and characterized by different techniques, including X-ray
structure determination, spectroscopic, and electrochemical measurements, as reported elsewhere. Herein, we report the interactions of these complexes, and corresponding free ligands, with human serum albumin (HSA) verifying their relative thermodynamic stability and differences in binding
to this protein. Interactions with HSA were verified by CD measurements monitored at 564 nm, up to stoichiometric ratio 2:1 [Complex]:[protein], according to competitive equilibria involving the insertion of copper at the selective N-terminal metal binding site in HSA, and additionally
at a secondary nonselective site. Further interactions of these complexes with L-tryptophan residues, and probable supplementary site(s) for the binding, were followed by fluorescence measurements. Analogous experiments with the free L and L′ indicated much weaker
interactions. Protein oxidation damage was observed for both complexes, monitored by carbonyl groups formation in the presence of H2O2, probably with the participation of reactive oxygen species. Density functional theory calculations exhibit metal-ligand binding interaction
energies similar to [Cu(HSA-Nterminal)]+, and reinforced the experimental results, showing clearly that such triazole ligands are competitive toward copper(II) in biological medium.
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Document Type: Research Article
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil;
L2CM UMR 7053 CNRS, Université de Lorraine, Faculté des Sciences, Vandoeuvre-lès-Nancy, France;
Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
Department of Chemistry, Virginia Commonwealth University, Richmond, VA, USA;
July 3, 2018