Interaction between Dioscin and Human Serum Albumin Analyzed by Molecular Docking Technique and Spectroscopy
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Abstract:
In this research, the mechanism of action of dioscin (DS) on human serum albumin (HSA) was investigated. The relationship between DS and HSA was investigated using dock 6.0 molecular docking methods, fluorescence emission spectroscopy and ultraviolet spectrophotometry. There were 8 binding modes between DS and HSA. On the combined basis of the Grid score and internal energy level, The 8th dominant conformation (with a Grid score as -75.9787 kcal/mol) was selected (in which the interactive force was hydrophobic interaction with the main bound amino acid residue being tryptophan Trp214). The fluorescence spectra revealed that with the increase of DS concentration, the HSA-DS fluorescence intensity decreased accompanied by a blue shift, indicating the quenching of the fluorescence of tryptophan (Trp) in HAS under the action of DS. The synchronous fluorescence detected under the conditions of wavelength difference Δλ=15 nm and Δλ=60 nm indicates the immediate changes in the surrounding environment of the Trp residue contained in HAS upon the binding of DS and HAS. The calculations based on the Stern-Volmer equation revealed that the bimolecular collision constant Kq was higher than 2.0×1010 L/mol·s and the static quenching binding constant Ka was higher than 5×104 L/mol. These findings confirmed that the quenching mechanism was static quenching involving hydrophobic interactions with one binding site, and were in agreement with the molecular docking results. The UV absorption spectra showed that an increase of DS concentration corresponded to an increased absorbance, indicating further the interactions between DS and HSA. Molecular docking and spectroscopy analyses showed that DS and HSA were bound mainly at the Trp214 position of tryptophan via hydrophobic interactions, and HSA underwent conformational and microenvironmental changes. The data obtained from this research clarify the mechanisms underlying the action of dioscin on HSA, and provide a new basis for further understanding of the effect of dioscin on protein function during its storage and transportation within the human body.
