Spectrofluorometric and computational approaches for the interaction studies of aclonifen and bifenox with human serum albumin

Interaction of two broadly used herbicides, aclonifen (ACF) and bifenox (BIF) with the major transporter in human circulation, human serum albumin (HSA) were examined using fluorescence and absorption spectral measurements combined with in silico analyses. Assessment of the fluorescence and absorption spectral results affirmed the complexation between ACF/BIF and HSA. Increase in the KSV value with temperature characterized the ACF/BIF-induced quenching of the protein fluorescence as dynamic quenching. The moderate binding af-finities (Kf = 1.74x104 - 1.95x106 M-1 for ACF-HSA complex; Kf = 2.00x103 - 1.02x106 M-1 for BIF-HSA complex) were pointed out between ACF/BIF and HSA, showing a relatively higher binding constant values with increasing temperatures. Quantitative evaluation of thermodynamic data (& UDelta;S = +0.86 kJ mol-1 K-1 and & UDelta;H = +225.43 kJ mol-1 for ACF-HSA complex; & UDelta;S = +1.11 kJ mol- 1 K-1 and & UDelta;H = +304.63 kJ mol-1 for BIF-HSA complex) predicted the contribution of hydrophobic interactions in the ACF-HSA and BIF-HSA association processes, which were well supported by our molecular docking results. In silico analyses were made to acquire insight details into the ACF and BIF binding to HSA at the binding sites and suggested the locations of ACF and BIF binding sites as both subdomain IIA (site I) and subdomain IIIA (site II) of HSA, showing more preference toward site I.

Automated summary

In this study, the interaction between two widely used herbicides, aclonifen (ACF) and bifenox (BIF), and the major transporter in human circulation, human serum albumin (HSA), was investigated using fluorescence and absorption spectral measurements combined with in silico analyses. The results confirmed the complexation between ACF/BIF and HSA, and the quenching of HSA fluorescence by ACF/BIF was found to be temperature-dependent. Thermodynamic data and molecular docking results suggested the contribution of hydrophobic interactions in the ACF-HSA and BIF-HSA association processes.