Binding of naringin and naringenin with hen egg white lysozyme: A spectroscopic investigation and molecular docking study

The interactions of naringenin (NG) and naringin (NR) with Hen Egg White Lysozyme.(HEWL) in aqueous medium have been investigated using UV-vis spectroscopy, steady-state fluorescence, circular dichroism (CD), Fourier Transform infrared spectroscopy (FT-IR) and molecular docking analyses. Both NG and NR can quench the intrinsic fluorescence of HEWL via static quenching mechanism. At 300 K, the value of binding constant (K-b) of HEWL-NG complex (5.596 +/- 0.063 x 10(4) M-1) was found to be greater than that of HEWL-NR complex (3.404 +/- 0.407 x 10(4) M-1). The negative Delta G degrees values in cases of both the complexes specify the spontaneous binding. The binding distance between the donor (HEWL) and acceptor (NG/NR) was estimated using the Forsters theory and the possibility of non-radiative energy transfer from HEWL to NG/NR was observed. The presence of metal ions (Ca2+, Cu2+ and Fe2+) decreased the binding affinity of NG/NR towards HEWL. Synchronous fluorescence studies indicate the change in Trp micro-environment due to the incorporation of NG/NR into HEWL CD and FT-IR studies indicated that the alpha-helicity of the HEWL was slightly enhanced due to ligand binding. NG and NR inhibited the enzymatic activity of HEWL and exhibited their affinity for the active site of HEWL Molecular docking studies revealed that both NG and NR bind in the close vicinity of Trp 62 and Trp 63 residues which is vital for the catalytic activity. (C) 2017 Elsevier B.V. All rights reserved.