Structural and dynamic features of Candida rugosa lipase 1 in water, octane, toluene, and ionic liquids BMIM-PF6 and BMIM-NO3.

Ionic liquids (ILs) and organic chemicals can be used as solvents in biochemical reactions to influence the structural and dynamic features of the enzyme, sometimes detrimentally. In this work we report the results for molecular dynamics simulations of Candida rugosa lipase (CRL) in ILs BMIM-PF6 and BMIM-NO3, as well as organic solvents toluene and octane in an effort to explore the role of solvent on the structure and dynamics of an enzyme known to be active in many nonaqueous media. Simulations of CRL in water were also included for comparison, bringing the aggregate simulation time to over 2.8 μs. At both 310 and 375 K the ILs significantly dampen protein dynamics and trap the system near its starting structure. Structural changes in the enzyme follow the viscosity of the solvent, with the enzyme deviating from its initial structure the most in water and the least in BMIM-PF6. Interactions between the enzyme surface and the solvent in the IL simulations show that contacts are dominated by the IL anion, which is ascribed to a broader spatial distribution of positively charged protein residues and reduced mobility of the cation due to the size of the imadazolium ring.