Analytical Sciences

Interaction between Alizarin and Human Serum Albumin by Fluorescence Spectroscopy

Feng GE, Lixiang JIANG, Diqiu LIU, and Chaoyin CHEN

School of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650224, P. R. China

The binding properties on alizarin to human serum albumin (HSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-visible absorbance spectroscopy. The results showed that alizarin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer occurred within the molecules. The number of binding sites was 1, and the efficiency of Förster energy transfer provided a distance of 1.83 nm between tryptophan and alizarin binding site. ΔH^θ, ΔS^θ and ΔG^θ were obtained based on the quenching constants and thermodynamic theory (ΔH^θ < 0, ΔS^θ > 0 and ΔG^θ < 0). These results indicated that hydrophobic and electrostatic interactions are the main binding forces in the alizarin-HSA system. In addition, the results obtained from synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that the binding of alizarin with HSA could induce conformational changes in HSA.

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