ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Interactions of antifouling monolayers: Energy transfer from excited albumin molecule to phenol red dye

Hui Xu, Robert Wallace, and Maria Hepel

Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA

E-mail: hepelmr@potsdam.edu

Abstract: Albumin, as an antifouling agent preventing non-specific adsorption, is widely applied in biosensor construction and in the design of nanocarriers for theranostic applications. However, albumin is not completely inert and it interacts with many endogenous and exogenous compounds. The present work investigates the interactions of bovine serum albumin (BSA) with phenol red dye (PR), a common component of cell-growth media. PR was found to bind to BSA, with the affinity constant KA = (2.5 ± 0.8) × 10⁵ L mol⁻¹, and that it quenches the intrinsic BSA fluorescence through the F¨orster non-radiative resonance energy transfer (FRET) via static modes, with critical FRET distance of R0 = 2.65 nm. Synchronous fluorescence spectroscopy measurements indicated a conformational transition of BSA in the presence of PR to a conformation with tyrosine residues surrounded by a more hydrophobic environment. Thermodynamic parameters, ΔH°, ΔG° and ΔS°, determined using fluorescence and isothermal titration microcalorimetry, indicated that entropic contribution played a major role at ambient temperature. It was also found that common metal ions increased KA but Ca²⁺ and Fe³⁺ decreased it.

Keywords: bovine serum albumin – BSA-phenol red binding – fluorescence energy transfer – BSA conformation change – thermodynamic properties – isothermal titration calorimetry

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0015

Chemical Papers 69 (1) 227–236 (2015)