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Abstract
Deep eutectic solvents (DESs) emerged as potential alternative solvent media in multiple areas, including biomolecular (cryo)preservation. Herein, we studied the stability of a small protein (ubiquitin) in water and a betaine-glycerol-water (B:G:W) (1:2:z; z = 0, 1, 2, 5, 10) DES, through molecular dynamics. An AMBER-based model that accurately describes the density and shear viscosity of the DES is proposed. We find that water molecules are largely trapped in the solvent, precluding the formation of a full hydration layer, seemingly opposite to osmolytes’ preferential exclusion/preferential hydration mechanism. Whereas the protein is stable in the DES, structural fluctuations are largely suppressed and only recovered upon sufficient hydration. This is explained by a solvent-slaving mechanism where -fluctuations are key, also explaining the non-monotonic folding of some proteins in aqueous DESs. A thermal stability enhancement in the DES is also observed, caused by a similar slowdown of the backbone torsional dynamics. Our results support a kinetic stabilization of the protein in the DES, whereas a possible thermodynamic stabilization does not follow a preferential hydration or water entrapment mechanism.
Supplementary materials
Title
Supporting Information
Description
Table S1-S5
Figure S1 - Molecular representation of Bet and Gly.
Figure S2 - Density and viscosity of the Bet:Gly DES as a function of λQ and λsigma.
Figure S3 - Bet-Bet, Bet-Gly, and Gly-Gly RDFs for the B:G (1:2) DES.
Figure S4 - Bet-Bet, Bet-Gly, Gly-Gly, Bet-OW, Gly-OW, and OW-OW RDFs for (B:G:W).
Figure S5 –Torsional dynamics for the alpha-helix of UBQ (phi).
Figure S6 – Torsional dynamics for the amino acids Asp32 and Glu34.
Figure S7 - Water coordination of the Calpha, C, and N.
Figure S8 - Rg of UBQ.
Figure S9 - SASA of UBQ.
Figure S10 – UBQ RMSD for replica 3 (R3).
Figure S11 – Torsional dynamics in aqueous DES (z = 5, 10) at 298 K and anhydrous (z = 0) DES (425 K and 450 K).
Figure S12 -Torsional dynamics for the alpha-helix of UBQ (phi).
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