Lysozyme stability in various deep eutectic solvents using molecular dynamics simulations

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Abstract
The ability of neat deep eutectic solvents (DESs) to influence protein structure and function has gained considerable interest due to the unstable nature of enzymes or therapeutic proteins, which are often exposed to thermal, chemical, or mechanical stresses when handled at an industrial scale. In this study, we simulated a model globular protein, lysozyme, in water and six choline chloride-based DES using molecular dynamics simulations, to investigate the structural changes in various solvent environments, giving insights into the overall stability of lysozyme. Root mean square deviation (RMSD) and root mean square fluctuations (RMSF) of the C-α backbone indicated that most DESs induced a less flexible and rigid lysozyme structure compared to water. The radius of gyration and end-to-end distance calculations pointed towards higher structural compactness in reline and levuline, while the structure of lysozyme considerably expanded in oxaline. Protein-solvent interactions were further analysed by hydrogen bonding interactions and radial distribution functions (RDF), which indicated a higher degree of lysozyme-hydrogen bond donor (HBD) interactions compared to lysozyme-choline hydrogen bonding. Surface area analysis revealed an overall % increase in total positive, negative, donor, and acceptor surface areas in malicine and oxaline compared to water and other DESs, indicating the exposure of a larger number of residues to interactions with the solvent. Reline, levuline, and polyol-based DESs comparatively stabilized lysozyme, even though changes in the secondary/tertiary structures were observed.Communicated by Ramaswamy H. Sarma.

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