Combined molecular docking, homology modeling and DFT method for the modification of bovine serum albumin (BSA) to improve fluorescence spectroscopy for phthalate acid esters chelated with BSA

Abstract

While phthalate acid esters (PAEs) cannot fluoresce alone, they can be detected by fluorescence spectroscopy after chelation with bovine serum albumin (BSA). In this study, the types of amino acid residues at the active site of PAEs chelated with BSA were determined using molecular docking technology. A modification scheme of BSA with higher detection sensitivity fluorescence spectroscopy for PAEs was proposed based on the docking results and constructed for a novel BSA structure with a higher detection sensitivity of fluorescence spectroscopy using a homologous modeling method. Density functional theory (DFT) was employed to explore the influence before and after BSA modification on PAEs’ detection through fluorescence spectroscopy. The results showed that the docking scores between BSAs and dimethyl phthalate (DMP), dibutyl phthalate (DBP) and di-n-octyl phthalate (DNOP) were increased up to 26.45%, 16.82% and 16.30%, respectively, indicating that the active site modification of BSA could enhance the binding affinity between BSA and PAEs. The fluorescence intensity of PAEs chelated with modified BSAs were calculated. The fluorescence intensity of fluorescence spectroscopy for DMP, DBP and DNOP chelated with BSAs after modification was increased up to 2.8-, 104.51- and 62.43-fold, respectively, which achieved the purpose of theoretically modifying BSA to improve the detection sensitivity of fluorescence spectroscopy for PAEs.