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

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