title: Spectroscopic investigation into the interaction of a diazacyclam-based macrocyclic copper(ii) complex with bovine serum albumin.
abstract: Cyclam-based ligands and their complexes are known to show antitumor activity. This study was undertaken to examine the interaction of a diazacyclam-based macrocyclic copper(II) complex with bovine serum albumin (BSA) under physiological conditions. The interactions of different metal-based drugs with blood proteins, especially those with serum albumin, may affect the concentration and deactivation of metal drugs, and thereby influence their availability and toxicity during chemotherapy. In this vein, several spectral methods including UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy techniques were used. Spectroscopic analysis of the fluorescence quenching confirmed that the Cu(II) complex quenched BSA fluorescence intensity by a dynamic mechanism. In order to further determine the quenching mechanism, an analysis of Stern-Volmer plots at various concentrations of BSA was carried out. It was found that the KSVvalue increased with the BSA concentration. It was suggested that the fluorescence quenching process was a dynamic quenching rather than a static quenching mechanism. Based on Förster's theory, the average binding distance between the Cu(II) complex and BSA (r) was found to be 4.98 nm; as the binding distance was less than 8 nm, energy transfer from BSA to the Cu(II) complex had a high possibility of occurrence. Thermodynamic parameters (positive ΔH and ΔS values) and measurement of competitive fluorescence with 1-anilinonaphthalene-8-sulphonic acid (1,8-ANS) indicated that hydrophobic interaction plays a major role in the Cu(II) complex interaction with BSA. A Job's plot of the results confirmed that there was one binding site in BSA for the Cu(II) complex (1:1 stoichiometry). The site marker competitive experiment confirmed that the Cu(II) complex was located in site I (subdomain IIA) of BSA. Finally, CD data indicated that interaction of the Cu(II) complex with BSA caused a small increase in the α-helical content. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Inorganic Chemistry Department, Faculty of Chemistry, Razi University, Kermanshah, Iran.|Medical Biology Research Center (MBRC), Kermanshah University of Medical Sciences, Iran.
authors.forename: Nahid
authors.initials: N
authors.lastname: Shahabadi
authors.affiliation: Department of Chemistry, Payame Noor University, 19395, -4697, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hakimi
authors.affiliation: Department of Chemistry, Payame Noor University, 19395, -4697, Tehran, Iran.
authors.forename: Teimoor
authors.initials: T
authors.lastname: Morovati
authors.affiliation: Inorganic Chemistry Department, Faculty of Chemistry, Razi University, Kermanshah, Iran.|Medical Biology Research Center (MBRC), Kermanshah University of Medical Sciences, Iran.
authors.forename: Saba
authors.initials: S
authors.lastname: Hadidi
authors.affiliation: Department of Chemistry, Payame Noor University, 19395, -4697, Tehran, Iran.
authors.forename: Keyvan
authors.initials: K
authors.lastname: Moeini
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006571:Heterocyclic Compounds; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D012710:Serum Albumin, Bovine; C024560:cyclam; D003300:Copper
keywords: bovine serum albumin; diazacyclam-based macrocyclic copper(II) complex; multi-spectroscopic methods; protein-metal complex interaction