Interaction studies of diazacyclam-based macrocyclic copper complex with bovine serum albumin (BSA): Spectroscopic investigations

In the present investigation, the interaction of a new macrocyclic copper(II) complex, [CuL]Br2, that L is 1,3,6,10,12,15-hexa aza tricyclo [13.3.1.16,10] eicosane with the transportprotein, bovine serum albumin (BSA), was studied in vitro under simulated physiologicalconditions using multi-spectroscopic methods. It is found that [CuL]Br2 has a strong ability toquench the intrinsic fluorescence of BSA through static quenching mechanism with a bindingconstant of about 104 M-1. Thermodynamic parameters (ΔH < 0 and ΔS < 0) and competitivefluorescence study with ANS, indicated that van der Waals force and hydrogen bonding playmajor roles in the binding of complex and BSA. Job’s plot result confirms that there is onebinding site in BSA for Cu(II) complex (1:1 stoichiometry). The displacement experiments indicate that the binding of [CuL]Br2 to BSA primarily occurred in the sub-domain IIA (siteI) of BSA. The results of circular dichroism (CD) and UV–vis spectroscopy showed that themicroenvironment of amino acid residues and the conformation of BSA were changed afteraddition of [CuL]Br2 complex.

Keywords:

Copper(II) complex , Diaza cyclam , Bovine serum albumin (BSA) , Fluorescence spectroscopy