Interaction mechanism of Cu+/Cu2+on bovine serum albumin: Vitro simulation experiments by spectroscopic methods

Copper (Cu) is an essential trace element for organisms, while excessive concentration of Cu is toxic. In order to assess the toxicity risk of copper in different valences, FTIR, fluorescence, and UV-vis absorption techniques were conducted to study the interactions between either Cu+ or Cu2+ and bovine serum albumin (BSA) under vitro simulated physiological condition. The spectroscopic analysis demonstrated that the intrinsic fluorescence emitted by BSA could be quenched by Cu+/Cu2+ via static quenching with binding sites 0.88 and 1.12 for Cu+ and Cu2+, respectively. On the other hand, the constants of Cu+ and Cu2+ are 1.14 x 103 L/mol and 2.08 x 104 L/mol respectively. Delta H is negative whereas Delta S is positive, showing that the interaction between BSA and Cu+/ Cu2+ was mainly driven by electrostatic force. In accordance with Fo center dot ster's energy transfer theory, the binding distance r showed that the transition of energy from BSA to Cu+/Cu2+ is highly likely to happen. BSA confor-mation analyses indicated that the interactions between Cu+/Cu2+ and BSA could alter the secondary structure of proteins. Current study provides more information of the interaction between Cu+/Cu2+ and BSA, and reveals the potential toxicological effect of different speciation of copper at molecular level.

Automated summary

FTIR, fluorescence, and UV-vis absorption techniques were used to study the interaction between Cu+ and Cu2+ and bovine serum albumin (BSA) under simulated physiological conditions. The spectroscopic analysis showed that Cu+/Cu2+ could quench the intrinsic fluorescence emitted by BSA through static quenching with binding sites of 0.88 and 1.12 for Cu+ and Cu2+ respectively. The interaction was mainly driven by electrostatic force, as indicated by the negative ΔH and positive ΔS values. This study provides insight into the toxicological effects of different speciation of copper at the molecular level.