Fluorescence signal switching of novel pyrenyl probe for the detection of bovine serum albumin

Abstract

In this study, a specific recognition element tagged with a fluorescent dye was developed for the detection of binding interaction with bovine serum albumin (BSA). A novel pyrenyl probe, ibuprofen-1-pyrenemethylamide (Py-IB), was designed and synthesized by attaching ibuprofen to the pyrenyl chromophore. The ibuprofen-derived pyrenyl probe caused switching of emissive signals of Py-IB from pyrene excimer to excited monomer upon binding to BSA. This switching behavior of Py-IB was not observed upon its binding to other tested proteins, such as lysozyme or lactoglobulin, indicating high selectivity and sensitivity of Py-IB to BSA. Visual detection under UV light of Py-IB/BSA solution showed the switching back from the monomer form to the excimer form in the presence of ibuprofen, indicating the binding competition of ibuprofen at Py-IB binding site. Photocleavage of BSA by Py-IB was achieved by activation of Py-IB/BSA solution with light at 346 nm, in the presence of cobalt (III) hexamine trichloride (CoHA) as an electron acceptor. Two new product bands were observed, and the cleavage site possibly occurred between Arg409 – Tyr410. Molecular docking study revealed a Py-IB binding site at subdomain IIIA on BSA, which confirmed the results from competitive study, with the lowest binding free energy of −10.17 kcal/mol. The studies showed that Py-IB was located in close proximity to hydrophobic residues in the binding pocket. The fluorescence signal switching of ligand upon binding to its target protein can be an easy way and very useful for monitoring ligand-biomolecular interaction.