Interaction Between Plumbagin and Human Serum Albumin by Fluorescence Spectroscopy

The interaction of plumbagin (PLU) with human serum albumin (HSA) in physiological buffer (pH=7.4) was studied by fluorescence spectroscopy. Results obtained from analysis of the fluorescence spectra indicated that PLU has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. Fluorescence quenching data revealed that the quenching constants (K) are 4.43x10(4), 3.26x10(4) and 1.69x10(4) L.mol(-1) at 293, 303 and 313 K, respectively. The thermodynamic parameters Delta H degrees and Delta S degrees were calculated to be -36.63 kJ.mol(-1), and -35.702 J.mol(-1).K(-1) respectively, which suggested that van der Waals interactions and hydrogen bonds play a major role in the interaction of PLU with HSA. The distance between donor (HSA) and acceptor (PLU) was calculated to be 3.76 nm based on Forster's non-radiative energy transfer theory. The results of synchronous fluorescence spectra showed that binding of PLU to HSA can induce conformational changes in HSA.