“Ultrafast 2D IR Spectroscopy of Membrane Peptide Systems”

Plasma membranes are the main liaisons between the intercellular and extracellular environment, playing a critical role in numerous biological processes. Recent research has challenged the long-standing “fluid mosaic model,” representing membranes as densely packed, heterogeneous environments. Within these complex membranes are transmembrane proteins which comprise up to 50% of the membrane mass, and are themselves diverse in sequence, structure, and function. Combining two-dimensional infrared spectroscopy (2D IR) and molecular dynamics simulations (MD), we have explored membrane complexity from two perspectives: first, we address the sequence heterogeneity in transmembrane peptides; and second, we explore the effect this crowded environment has on the lipids themselves and the implications this has on future membrane studies.

Site-specific 2D IR has been used to directly study localized hydration effects in a lipid membrane upon insertion of pH (Low) Insertion Peptide (pHLIP), a model membrane peptide. Semi-quantitative results indicate enhanced water penetration in the membrane core concurrent with peptide insertion, suggesting the abundance of hydrophilic residues in the pHLIP sequence drives membrane hydration. Further, crowding experiments have probed ultrafast dynamics at the lipid-water interface of model membranes as a function of transmembrane peptide concentration, revealing a non-monotonic dependence on peptide concentration linked to interfacial water structure.

Zoom link: https://umich.zoom.us/j/99088330811