It turns out that the electrostatic forces associated with water alter the vibrational frequencies and lifetimes of peptide backbones.  We will report 2D IR spectroscopic measurements of the amide I vibrational mode, in which the 2D IR lineshapes and lifetimes have been measured.  From the linewidths, we extract the inhomogeneous distribution to gain a measure of hydration and backbone structural disorder.  Utilizing vibrational lifetimes, we are able to improve the resolution of 2D IR spectroscopy by discriminating against disordered structures.  Using isotope labeling, these measurements are made residue-by-residue.  Using this approach, we will show results in which we have studied the structure and environment of an antibiotic surface bound membrane polypeptide, a transmembrane alpha-helical bundle, an amyloid fiber and an ion channel.  We find that the amide I linewidths are sensitive even to the few waters inside the ion channel.

Mapping water in proteins with 2D IR spectroscopy

246th National Meeting (2013)

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