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In this work, we investigated the effects of carboxybetaine (CB) and (ethylene glycol)4 (EG4) solutes on chymotrypsin inhibitor 2 (CI2) as a model protein using molecular dynamics simulations. The properties studied include the radial distribution functions of these two solutes to the C-α atoms of the 64 residues of CI2, the average numbers of solute-protein and water-protein hydrogen bonds, the root mean square deviation of the C-α atoms of the protein, and the solvent access surface area of the protein. Results show that these two solutes share some common properties while have some different effects on the protein. Both of these two solutes do not accumulate preferentially near the protein and CI2 is folded with either of them. However, CI2 is found to have properties in the CB solution closer to bulk water, whereas CI2 shows reduced flexibility and decreased SASA of the hydrophobic domain in the EG4 solution. Although the protein is folded with both CB and EG4, superhydrophilic CB has a minimal effect on the protein due to the shared zwitterionic nature of both CB and protein whereas amphiphilic EG4 alters the properties of the protein via hydrophobic interactions. [ABSTRACT FROM AUTHOR]

This work investigates the effect of zwitterionic molecules on ionic association in ethylene oxide (EO)-based electrolytes using molecular dynamics simulations. Zwitterionic molecules can associate with cations and anions because they possess both positively and negatively charged groups. This unique feature can be leveraged to develop electrolytes with high ionic conductivity if we understand how zwitterionic molecules influence ionic associations. We investigate the ionic associations in the electrolytes composed of oligo(ethylene oxide) (EO) (EO x , x = 2, 3, 4, and 5), LiTFSI and zwitterionic molecules containing cationic imidazole group and anionic sulfonate group using molecular dynamics simulations. The analyzed properties include the radial distribution functions between Li+, [TFSI]-, EO x and zwitterionic molecules, the structures and dynamics of Li+-[TFSI]-, Li+- EO x and Li+-zwitterion associations, and the diffusion coefficients of Li+, [TFSI]-, EO x and zwitterionic molecules. The simulation results show two distinct effects of zwitterionic molecules on ionic associations in the electrolytes. First, they could release Li+ from the trapping effect of EO x chains and accelerate Li+ transport. Second, they can associate with Li+ themselves and slow down the Li+ transport. The competition between these two effects relates to the length of the EO x chains. Our simulations suggest that zwitterionic molecules could help manipulate the ionic conductivity of polyethylene oxide electrolytes. Image 1 [ABSTRACT FROM AUTHOR]