It is well known that tryptophan (Trp) plays an important role in anchoring various membrane peptides and proteins into lipid bilayers. In addition, Trp residues are critical towards the self-assembly and function of a number of ion channels. However, the indole ring of Trp lacks a strong and convenient infrared (IR) transition that can be exploited to study the local structure and dynamics of membrane proteins using IR spectroscopy. Herein, we demonstrate that the CN stretching vibration of a nitrile-derivatized Trp analog, 5-cyanotryptophan, is a useful IR probe for this purpose. Specifically, we will discuss, using the transmembrane domain of the influenza A M2 proton channel as an example, how this probe, in conjunction with several linear and non-linear IR spectroscopic techniques, can be used to site-specifically determine the orientation, hydration state, and dynamics of Trp residues in membrane peptides and proteins.

Using infrared measurements to probe the structure and local environment of membrane proteins

251st National Meeting (2016)

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