Characterization of protein secondary structures at interfaces in situ and in real time is important to understand biological processes associated with cell membranes and solve problems in various fields of biomedical sciences. However, such characterization is challenging because it requires methods that are both selective to interfaces and protein secondary structures. We demonstrate that chiral sum frequency generation spectroscopy (SFG) can provide peptide amide I and N-H stretch vibrational signals that are free of water background and characteristic to parallel beta-sheet, anti-parallel beta-sheet, alpha-helix, 3-10 helix and disordered structures. Hence, chiral SFG can distinguish protein secondary structures at interfaces. Using chiral SFG, we monitored misfolding of an amyloid protein, characterized protein orientation at interfaces, developed new methods for probing proton exchange in proteins, and studied two-dimensional crowding effects on protein folding at interfaces. These studies demonstrate that chiral SFG is a new spectroscopic tool for characterizing protein structures and functions at interfaces and can be used to address a wide range of fundamental and engineering problems.

Chiral sum frequency generation spectroscopy for protein characterization at interfaces

255th National Meeting (2018)

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