Conformation change of trypsin induced by acteoside as studied using multiple spectroscopic and molecular docking methods

ABSTRACTThe interaction of trypsin with acteoside was studied using ultraviolet visible absorption, fluorescence, synchronous fluorescence, circular dichroism techniques, along with molecular docking method. The fluorescence experiments indicated that acteoside quenched the intrinsic fluorescence of trypsin via a combined quenching process (static and dynamic quenching). The binding constant of acteoside to trypsin obtained was 2.50 × 105 L mol−1 at 298 K and the number of binding site was about one under the same experimental condition. The thermodynamic functions ΔH° and ΔS° of the binding process were 8.79 kJ mol−1 and 132.58 J mol−1 K−1, respectively, which indicated that the hydrophobic force was the main acting force between them. Ultraviolet–visible, synchronous fluorescence together with circular dichroism spectra studies demonstrated that the interaction of acteoside with trypsin lead to a loosening and unfolding of the protein backbone with partial β-sheet structures being transformed into α-hel...