Fluorescence quenching of bovine serum albumin by NNMB

A new type of fluorophore 2-(naphthalen-1-yl)-1-((naphthalen-1-yl)methyl)-1H-benzimidazole (NNMB) has been prepared and characterized by 1H NMR, 13C NMR, mass and IR spectral analysis. Absorption, fluorescence and synchronous fluorescence spectral studies have been made for the mutual interaction of NNMB with bovine serum albumin (BSA). Absorption spectroscopy proved the formation of a ground state BSA…NNMB complex. Fluorescence spectrum of BSA in the presence of NNMB clearly shows that NNMB acts as a quencher. Based on the theory of Forester’s non-radiation energy transfer (FRET) binding distance has been deduced. The Stern–Volmer quenching constant (KSV), binding site number (n), apparent binding constant (KA) and corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were determined.

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► The interactions between NNMB and BSA were investigated.
► Fluorescence quenching arises from the formation of BSA–NNMB complex.
► Fluorescence spectra to exploit the structural change of BSA.
► Thermodynamic parameters were determined.