Human serum albumin interaction with paraquat studied using spectroscopic methods

The interaction between herbicide paraquat and human serum albumin (HSA) was investigated by fluorescence and UV/Vis absorption spectroscopy. Paraquat can strongly quench the intrinsic fluorescence of HSA by static quenching and nonradiative energy transferring: The hydrophobic and electrostatic interactions play a major role in stabilizing the complex. The binding site number n and apparent binding constant K-A, corresponding thermodynamic parameters Delta G, Delta H, Delta S at different temperatures, were calculated. The distance r between donor (HSA) and acceptor (paraquat) was obtained according to fluorescence resonance energy transfer. The effect of paraquat on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy. (c) 2006 Elsevier Inc. All rights reserved.