Fluorescence resonance energy transfer between bovine serum albumin and fluoresceinamine

Physical binding‐mediated organic dye direct‐labelling of proteins could be a promising technology for bio‐nanomedical applications. Upon binding, it was found that fluorescence resonance energy transfer (FRET) occurred between donor bovine serum albumin (BSA; an amphiphilic protein) and acceptor fluoresceinamine (FA; a hydrophobic fluorophore), which could explain fluorescence quenching found for BSA. FRET efficiency and the distance between FA and BSA tryptophan residues were determined to 17% and 2.29 nm, respectively. Using a spectroscopic superimposition method, the saturated number of FAs that bound to BSA was determined as eight to give a complex formula of FA₈–BSA. Finally, molecular docking between BSA and FA was conducted, and conformational change that occurred in BSA upon binding to FA molecules was also studied by three‐dimensional fluorescence microscopy. Copyright © 2015 John Wiley & Sons, Ltd.