Molecular investigation of the interaction between ionic liquid type gemini surfactant and lysozyme: A spectroscopic and computational approach

Herein, we are reporting the interaction of ionic liquid type gemini surfactant, 1,4-bis(3-dodecylimidazolium-1-yl) butane bromide ([C12−4-C12im]Br2) with lysozyme by using Steady state fluorescence, UV-visible, Time resolved fluorescence, Fourier transform-infrared (FT-IR) spectroscopy techniques in combination with molecular modeling and docking method. The steady state fluorescence spectra suggested that the fluorescence of lysozyme was quenched by [C12−4-C12im]Br2 through static quenching mechanism as confirmed by time resolved fluorescence spectroscopy. The binding constant for lysozyme-[C12−4-C12im]Br2 interaction have been measured by UV-visible spectroscopy and found to be 2.541 × 105M−1. The FT-IR results show conformational changes in the secondary structure of lysozyme by the addition of [C12−4-C12im]Br2. Moreover, the molecular docking study suggested that hydrogen bonding and hydrophobic interactions play a key role in the protein-surfactant binding. Additionally, the molecular dynamic simulation results revealed that the lysozyme-[C12−4-C12im]Br2 complex reaches an equilibrium state at around 3 ns. © 2015 Wiley Periodicals, Inc. Biopolymers 103: 406–415, 2015.