Abstract
By using spectroscopic methods, we probed the interaction of Ag + with bovine serum albumin (BSA) in an aqueous environment. Fluorescence of BSA quenched by Ag + is a dynamic quenching process. Two binding modes–a strong one at low concentration of Ag + and a weak one at high concentration were found. The association constant ( K A) and the number of binding sites ( n) were 4.88 × 10 3 M − 1 and 1.17 for strong binding, and 17.6 M − 1 and 0.547 for weak binding at 293 K. The results of thermodynamic parameters Δ H θ , Δ G θ and Δ S θ for instinct binding modes at different temperatures indicated that the hydrogen bonding and van der Waals interaction play a major role for low Ag +/BSA ratio while electrostatic association for high Ag +/BSA ratio. Data of UV–Vis and Circular dichroism (CD) suggested that with the increasing amount of Ag +, the secondary structure undergoes a decrease in α-helix and an increase in β content and the backbone of BSA experiences a micro-environmental alteration. Furthermore, the distance r between donor (Trp-212) and acceptor (Ag +) was evaluated to be 10 nm according to nonradiative energy transfer theory.
Published Version
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