Förster resonance energy transfer between pyrene and bovine serum albumin: Effect of the hydrophobic pockets of cyclodextrins

The phenomenon of Förster resonance energy transfer (FRET) between pyrene and bovine serum albumin (BSA) protein in presence of cyclodextrins (CDs) is explored in the present work. CDs provide hydrophobic environment and thus the aromatic molecules get encapsulated in them depending on the relative size and space. In this work we revealed that along with pyrene monomer, the side chains of amino acids in BSA can get trapped partly in the hydrophobic cavities of CDs if space permits. While being encapsulated by β-CD as pyrene monomer, it can interact with the BSA tryptophan moiety exposed toward the aqueous environment to form a dimer through π–π interaction. This, in turn, affects the energy transfer process by reducing the efficiency. On the other hand, pyrene excimer gets encapsulated in a γ-CD molecule due to availability of enough space. The excimer shows a new band at a higher wavelength. This further reduces FRET efficiency due to scarcity of acceptor for the tryptophan moieties in BSA.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► FRET between pyrene and bovine serum albumin in cyclodextrins (CDs) is explored. ► Aromatic molecules get encapsulated in hydrophobic CD cavities depending on size. ► Pyrene monomer as well as the amino acid side chains of BSA can get trapped in CDs. ► FRET efficiency between pyrene monomer and tryptophan in BSA gets reduced in CDs. ► In γ-CD FRET is further reduced due to formation of pyrene excimer.