Complex of nicosulfuron with human serum albumin: A biophysical study

Nicosulfuron is a sulfonylurea herbicide developed by DuPont that has been used successfully for weed control in maize. The binding mechanism and binding site identified in human serum albumin (HSA) with the use of fluorescence, circular dichroism (CD) and molecular modeling is the subject of this paper. From the CD, synchronous and three-dimensional fluorescence results, it was apparent that the interaction of nicosulfuron with HSA caused secondary structure changes in the protein. Fluorescence data revealed that the nicosulfuron induced the fluorescence quenching of HSA through a static quenching procedure. Thermodynamic analysis results implied the role of hydrophobic and hydrogen bonds interactions in stabilizing the nicosulfuron–HSA complex. Site marker competitive experiments showed the binding of nicosulfuron to HSA primarily took place in subdomain IIA (Sudlow’s site I), this corroborates the guanidine hydrochloride (GuHCl) induced denaturation of HSA, hydrophobic probe ANS displacement and molecular modeling results. In this work, the presented binding research extends our knowledge of the binding properties of sulfonylurea herbicides to the important plasma protein HSA.