Elucidation of interactions of BSA with [EPMpyr]+[Cl]− using spectroscopic techniques with reference to theoretical thermodynamic and molecular docking studies

Abstract

On the premise that bovine serum albumin (BSA) is a suitable substitute for Human Serum Albumin (HSA) in experiments, its interactions with ionic liquid (IL), N‑2′,3′‑epoxypropyl‑N‑methyl‑2‑oxopyrrolidinium chloride, ([EPMPyr]{Cl}), was studied. This was done on the basis that the data would give information on the potential role of ionic liquids (ILs) in drug delivery, involved in the treatment of diseases. This was effected by eliciting data from the interactions using UV–visible absorption, emission spectroscopy, circular dichroism (CD), FTIR and molecular docking. The subsequent changes in microenvironment around the tryptophan (Trp) residues in BSA were observed using fluorescence spectroscopy techniques. Furthermore, UV and CD results indicated that the secondary structure of BSA was affected by interaction of IL at high concentrations and temperatures. In addition, the thermophysical and thermodynamic studies were used to evaluate the thermostability of BSA on interaction with IL at various concentrations. These thermophysical and thermodynamic values provided evidence that interactions such as H-bond, dipole, and non-covalent interactions occured in the BSA-IL system. This is attributed, mainly, to hydrophobic and electrostatic interactions resulting in the unfolding of polypeptides within BSA. Therefore, the hydrogen bonding interaction and cation-protein interactions are the driving processes for strong binding between BSA and the IL. Furthermore, molecular docking shows that the entry of IL into subdomains of protein is due to the cationic moiety of oxopyrrolidine interacting with the hydrophobic residues of the domains.