Spectroscopic analysis of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol binding to blood plasma albumin

Binding of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol (Cl), a biologically active substance, to bovine blood plasma albumin (BSA) at 293, 298, and 303 K was studied using fluorescence (steady state, synchronous, excitation/emission matrix) and FT-IR spectroscopy methods. The experimental results showed that Cl causes fluorescence quenching of BSA through both static and dynamic quenching mechanisms. The thermodynamic parameters, enthalpy and entropy change, for the static quenching were calculated to be- 35.73 kJ mol(-1) and - 35.34 J mol(-1) K-1, which indicated that hydrogen bonding and van der Waals interactions were the predominant intermolecular forces regulating C1-BSA interactions. Distance between donor and acceptor (2.14, 2.26, and 2.30 nm) depending on the temperature, obtained from intrinsic Forster resonance energy transfer calculations, revealed the static quenching mechanism of BSA fluorescence in 0-3.0 x 10(-5) mol/dm(3) concentration range of Cl. The micro-environmental and conformational changes in BSA structure, established by synchronous, excitation/ emission matrices and FT-IR spectra showed the changes in the BSA secondary structure. [GRAPHICS] .