In vitro study on the binding of herbicide glyphosate to human serum albumin by optical spectroscopy and molecular modeling

In this study, the interaction mechanism of herbicide glyphosate and human serum albumin (HSA) has been characterized by fluorescence, UV, Fourier transform infrared (FT-IR), Circular dichroism (CD) spectroscopic and molecular modeling methods. The structural characteristics of glyphosate and HSA were probed, and affinity constants were determined under different temperatures. The enthalpy change (Delta H degrees) and the entropy changes (Delta S degrees) were calculated to be -21.78 kJ mol(-1) and 6.38 Jmol(-1) K-1 according to the Van't Hoff equation. These results indicated that glyphosate binds to HSA mainly by hydrogen bond and hydrophobic interaction can also not be excluded, which is in good agreement with the results from modeling experiment. The average binding distance, r, between the donor (HSA) and the acceptor (glyphosate) was evaluated and found to be 2.89 nm according to the Forster's theory of non-radiation energy transfer. The alterations of protein secondary structure in the presence of glyphosate were confirmed by the evidences from UV, FT-IR and CD spectroscopes. (c) 2007 Elsevier B.V. All rights reserved.