Using model compounds, the behavior of the infrared absorption asymmetric stretching peak of a covalently bound azido group has previously been characterized, indicating that the peak is sensitive to the hydrogen bond density of the local environment, but not to the local electrostatics.  Thus, the asymmetric azido stretching mode frequency is a simple indicator of its local hydration environment.  To determine whether the azido group disrupts secondary structure formation, a model helical peptide labeled with a single azido group was used. The response of the azido probe group in the helical peptide is investigated here in solutions composed of varying ratios of 2,2,2-trifluoroethanol (TFE) and water.  TFE putatively induces helices by selective dehydration of the peptide near the amide backbone, and the azido stretching frequency can distinguish between TFE and water despite TFE's strong H-bond donor ability. A series of peptides with azido groups on increasingly extended artificial side chains provides information about hydration, both near the backbone of the peptide and in successively remote solvation layers.

Azido groups as site specific IR probes of hydration in model helical peptides

244th National Meeting (2012)

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