How Pure and Hydrated Reline Deep Eutectic Solvents Affect the Conformation and Stability of Lysozyme: Insights from Atomistic Molecular Dynamics Simulations.

Factors governing the stability and activity of proteins and enzymes in nonaqueous solvents have just been started to be explored. Because of their benign and economically viable nature, deep eutectic solvents (DESs) are being seen as an alternative media in many biotransformation processes. The present study exploits the changes in the conformation and stability of hen egg white lysozyme (HEWL) in the presence of reline (a eutectic mixture of choline chloride and urea) and reline/water mixtures using atomistic molecular dynamics simulations. The lysozyme structure was found to be partially folded in both reline and reline/water mixtures. Root-mean-square deviation (RMSD) of the positions of Cα atoms of lysozyme indicate that 50/50 reline/water solvent induces more destabilization in the conformation of HEWL than that by pure reline and 75/25 reline/water mixture. From the root-mean-square fluctuation (RMSF) analysis, it is found that the lysozyme active site (Glu35-Asp52) is quite stable in the presence of pure reline but it is least stable in the presence of 50/50 reline/water mixture. Our results show that the secondary structure of the lysozyme is significantly affected in the presence of reline. Our further analysis reveals that the hydrogen bonding interaction between HEWL-[Ch]+ dominates over HEWL-urea and HEWL-Cl- in pure reline than in reline/water mixtures.