Unveiling the binding details of berberine mid-chain fatty acid salts on lysozyme: Multi-spectroscopy and molecular...

The interactions of three berberine mid-chain fatty acid salts ([BBR][C_n], n = 6, 7, 8) with lysozyme (Lyz) are investigated in detail using multi-spectroscopic and molecular docking techniques. Steady-state fluorescence and UV-visible absorption experiments suggest that the binding mechanism of [BBR][C_n] on Lyz is a static quenching with a binding ratio of 1:1. The compound [BBR][C_n] exhibits a moderate binding affinity toward Lyz. The findings from UV-vis, synchronous fluorescence, three-dimensional fluorescence and FT-IR spectral measurements manifested the alternation in the secondary structure, microenvironment and conformation of Lyz by the binding of [BBR][C_n]. The α-helix content of Lyz declines, while the β-sheet content increases. The theory of Förster resonance energy transfer (FRET) was employed to measure the molecular distance between Lyz and [BBR][C_n]. Thermodynamic parameters and molecular docking results indicate that hydrophobic interaction, van der Waals force, and hydrogen bond are the primary driving forces during the binding process. The binding event enhances the esterase-like activity of Lyz. Furthermore, the binding affinity is influenced by environmental factors such as pH and temperature, as well as the anionic alkyl chain length of [BBR][C_n].