Biomass pretreatment with certain ionic liquids (IL) can be highly effective at generating a substrate that can be easily saccharified into fermentable sugars with high yields. In order to improve overall process economics, using mixtures of these ILs with water are more favored over the use of anhydrous IL; however, the solvent property of IL-water mixtures and correlations between cellulose digestibility, cellulose solvation and lignin depolymerization during IL-water pretreatment of lignocellulosic biomass are not well understood. We investigated pretreatment of switchgrass with mixtures of 1-ethyl-3-methylimidazolium acetate, [C 2 mim] [OAc], and water at 160°C. Results indicate that the chemical composition and crystallinity of the pretreated biomass, and the corresponding lignin dissolution and depolymerization, were dependent on [C 2 mim][OAc] concentration that correlated strongly with cellulose digestibility. In addition, the hydrogen bond basicity of the [C 2 mim][OAc]-water mixtures was found to be a good indicator of cellulose dissolution, lignin depolymerization, and sugar yields. Molecular dynamics simulations provided molecular level explanations on cellulose I β dissolution at different [C 2 mim][OAc]-water loadings. The knowledge gained from this study provides a better understanding of the duality of water as a co-solvent/anti-solvent in dissolving cellulose and serves as a design basis for the targeted design of ILwater mixtures that are effective at biomass pretreatment.

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Classical molecular dynamics (MD) simulation has been carried out in an explicit solvent environment to understand the interaction between the single walled carbon nanotube (SWCNT) and α-helix. A polyalanine peptide consisting of 40 alanine residues has been chosen as the model for the α-helix (PA(40)). Results reveal that the SWCNT induces conformational changes in PA(40). Furthermore, breakage of hydrogen bonds in the chosen model peptides has been observed, which leads to conformational transitions (α → turns) in different parts of the PA(40). Owing to these transitions, regions of different structural and energetic stability are generated in PA(40) which enable the PA(40) to curl around the surface of the SWCNT. The overall observations obtained from the MD simulations are not significantly influenced by the starting geometry and the choice of the force field. Although the qualities of structural information obtained from the MD simulation using ff03 and OPLS are different, the overall observation derived from the ff03 is similar to that of OPLS. Results from the MD simulation on the interaction of the α-helical fragment of the SNARES protein with the SWCNT elicit that the amino acid composition influences the interaction pattern. The wrapping of the α-helical fragment of the SNARES onto the SWCNT is similar to that of PA(40). Overall, there is a considerable decrease in the helical content of peptides upon interaction with SWCNTs, in agreement with the experimental findings.

Ab initio and density functional methods have been employed to study the structure, stability, and spectral properties of various ethylene glycol (EG(m)) and ethylene glycol-water (EG(m)W(n)) (m = 1-3, n = 1-4) clusters. The effective fragment potential (EFP) approach was used to explore various possible EG(m)W(n) clusters. Calculated interaction energies of EG(m)W(n) clusters confirm that the hydrogen-bonding interaction between EG molecules is perturbed by the presence of water molecules and vice versa. Further, energy decomposition analysis shows that both electrostatic and polarization interactions predominantly contribute to the stability of these clusters. It was found from the same analysis that ethylene glycol-water interaction is predominant over the ethylene glycol-ethylene glycol and water-water interactions. Overall, the results clearly illustrate that the presence of water disrupts the ethylene glycol-ethylene glycol hydrogen bonds.