Interaction between a novel intramolecular charge transfer fluorescent probe PFEP and human serum albumin

The interaction mechanism between human serum albumin (HSA) and 1-phenyl-3(fluorenone-2-yl)-5-(9-ethylcarbazole-3-yl)-2-pyrazoline (PFEP) was investigated by fluorescence and absorption titration techniques in combination with molecular modeling method. Stern–Volmer plots at different temperatures proved that PFEP could quench the intrinsic fluorescence of HSA attributed to a static quenching procedure. The association constants were calculated in the range of 1 × 105–8 × 105 mol−1 at different pH conditions, and the stoichiometric ratio of binding was 1:1 between PEEP and HSA. Molecular modeling study showed that the distance between indole moiety of the Trp214 residue and the carbazole group at the terminal of PFEP was 4.45 Å in the optimal model.