Vibrational  probe groups on native and artificial side chains can report on the  dipolar and hydrogen bonding characteristics of their immediate  environments, which are often remote from the peptide backbone.  However, the response of some side chain vibrations can report the  formation of secondary structure, especially the formation of helices,  upon protein and peptide binding events. The CN stretching band of the  modified amino acid cyanylated cysteine can show helical structure in  two ways: via frequency shift when excluded from the solvent, and via  lineshape changes when solvent-exposed throughout a structure formation  event. The asymmetric NNN stretch of artificial azido-derivatized amino  acids is sensitive only to water exposure, while selected C-D  vibrations on otherwise unmodified histidine side chains can report the  formation of inter-side-chain contacts that can hold secondary  structures together.  The use of these vibrations to report structure  formation in both protein-peptide and peptide-membrane binding events  will be discussed.

Local structure formation reported by vibrational probes on side chains

243rd National Meeting (2012)

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