Rhenium(I)-based fluorescence resonance energy transfer probe for conformational changes of bovine serum albumin

Protein binding properties of fac-rhenium(I) complexes with general structure [Re(CO)3(N-N)L]PF6, where N-N = 4,4′-dinanoyl-2,2-bipyridine and L = py-3-COOH (1a) and py-3-CONH2 (1b) with bovine serum albumin (BSA) were investigated at physiological pH (7.4) using UV–visible absorption and fluorescence spectral study, excited state lifetime measurement and circular dichroism (CD). The results observed from fluorescence spectra reveal the energy transfer from BSA to Re(I) complex, and the distance r between donor (BSA) and acceptor (Re(I) complex) is 3.05 nm and 2.16 nm for 1a and 1b respectively according to Forster's non-radiative energy transfer theory. CD results show that the binding of Re(I) complex could induce the conformational change with the loss of α-helicity.

Graphical abstractThe interaction between Re(I) complex and bovine serum albumin (BSA) in aqueous medium at pH 7.4 leads to the energy transfer from BSA to Re(I) complex.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The work presented in this manuscript involves an energy transfer between bovine serum albumin (BSA) and rhenium(I) complexes in aqueous’ medium. ► This is the first report on the binding accompanying energy transfer of these Re(I) complexes with bovine serum albumin. ► The results obtained from absorption, emission, lifetime and CD spectra show that these Re(I) complexes can be used as a class of probe for biophysical studies of macromolecules.