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 (K(sv)) were 2.78 × 10(4), 2.52 × 10(4), and 2.32 × 10(4) at 301, 310, and 318 K respectively. The Stern-Volmer quenching constant (K(sv)), binding site number (n), apparent binding constant (K(A)) 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 Cu(2+), Zn(2+), Ca(2+), Mg(2+), Ni(2+), Co(2+), and Fe(2+) on the binding constants between the FPPI and BSA were also studied.