Ionic liquids (ILs) are well known to cause a range of interesting effects on proteins and enzymes; however, here is still much to be done to understand the molecular scale mechanisms of these processes. Using molecular dynamics (MD), we have studied how several IL solutions change the structure and behavior of two short, model, Leucine-Lysine (LK) composed peptides at a hydrophobic interface.  These peptides - LKalpha14 and LKbeta15 - have been researched extensively through experiment and simulations in water, but have not yet been examined when exposed to ILs.  In our study we found that the two 50% 1-Butyl-3-methylimidazolium solutions we tested had a substantial effect on both the secondary structure and surface affinity of our peptides when compared to water.  IL solutions reduced the adsorption affinity of both LKalpha14 and LKbeta15 for the interface, while also preventing LKbeta15 from forming extended beta sheet structures.  In place of these beta sheet structures, we observed the formation of a L-alpha-like helix for lone LKbeta15 peptides at the interface.  IL presence also had a subtle effect on LKalpha14’s strong alpha helical character, reducing it for interface bound peptides and increasing it for peptides in bulk solution.  This work provides several new testable hypothesis about IL action on biomolecule structure that can be studied in detail using surface techniques such as sum frequency generation (SFG) spectroscopy.

LK-peptide structural and behavioral changes in ionic liquid solvents

251st National Meeting (2016)

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