Fluorescence investigation of the interaction of 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole with bovine serum albumin

The interaction between 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole (FPPI) and bovine serum albumin (BSA) was investigated by fluorescence spectral studies. The observed experimental result shows that the imidazole derivative has strong ability to quench the fluorescence of BSA by forming complex which is stabilized by electrostatic interactions. The effective quenching constants (Ksv) were 2.78 × 104, 2.52 × 104, and 2.32 × 104 at 301, 310, and 318 K respectively. The Stern–Volmer quenching constant (Ksv), binding site number (n), apparent binding constant (KA) and corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were calculated. The distance between the donor (BSA) and acceptor (FPPI) was obtained according to fluorescence resonance energy transfer (FRET). Conformational changes of BSA were observed from synchronous fluorescence technique. The effect of metal ions such as Cu2+, Zn2+, Ca2+, Mg2+, Ni2+, Co2+, and Fe2+ on the binding constants between the FPPI and BSA were also studied.

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► Interactions between FPPI and BSA were investigated by fluorescence quenching.
► Quenching mechanism arise from the formation of BSA–FPPI complex.
► Synchronous fluorescence spectra to exploit the structural change of BSA.
► The effect of other ions on the binding constants between FPPI and BSA.