Unraveling the binding characteristics of the anti-HIV agents abacavir, efavirenz and emtricitabine to bovine serum albumin using spectroscopic and molecular simulation approaches

Abstract

In the present study the binding characteristics of abacavir (ABV), efavirenz (EFV) and emtricitabine (EMC) to bovine serum albumin (BSA) have been investigated via the use of spectroscopic tools and in silico docking studies. Those ligands were found to statically quench the intrinsic fluorescence of BSA with binding constants ranging between 1.75 and 2.36×104Lmol−1 over the studied temperatures. Fluorescence quenching results were further interpreted to obtain the thermodynamic features of the interactions which revealed spontaneous interactions between the studied ligands and BSA with ΔH° values of −10.50, −2.56 and −2.89kJmol−1 and ΔS° values of of 47.46, 74.14 and 71.88 Jmol−1K−1 for ABV, EFV and EMC, respectively. Synchronous fluorescence measurments showed that the intrinsic fuorescence of BSA was being quenched by the 3 ligands with a suggested alteration in the microenvironments around the tyrosine residues of the BSA upon binding to ABV and EMC. Furthermore, markers of the BSA binding sites were incorportated to identify the binding site(s) on BSA for ABV, EFV and EMC. It was found that ABV and EMC bind to Sudlow sites I and II on the BSA while EFV binds only to site I which was further supported with the molecular docking findings.