Watching molecular motion at interfaces

In this thesis, the reorientational dynamics at interfaces for a model biophysical system and for an aqueous mineral surface are investigated. Side chain dynamics of proteins at interfaces are important for a wide range of processes ranging from protein binding to surfaces to stem cell growth. To this end, surface sensitive time- and polarization- resolved SFG supported by molecular dynamics simulations is used to first determine how L-leucine monomers adsorbed at the air-aqueous interface reorient. The monomers are found to reorient diffusively, and next similar methodology is used to study the reorientational dynamics of leucine side chains within model leucine lysine LK peptides adsorbed to the air water interface as a function of protein secondary structure. The hydrophobic side chain dynamics for 310 helical, α-helical, and β-strand LK peptides are found to be independent of secondary structure. Finally, the thesis concludes by presenting work at the buried silica-water interface. It is shown through phase resolved SFG that there are non-hydrogen bonded water species present at the interface. The reorientational and vibrational dynamics of this species are subsequently measured and are found to be similar to those of the free OH at hydrophobic interfaces.