Functional groups with unique frequencies in the infrared (i.e. azides, nitriles) have been used relatively broadly in the IR to provide site-specific probes of structure and dynamics in many chemical and biochemical systems.  There are several other functional groups with unique frequencies, but their weak IR absorption has made them less attractive as IR probes. Alkynes have been implemented as Raman imaging probes due to their large Raman scattering cross-sections, but the solvatochromism of the C≡C stretch has remained largely unexplored.  We have recently shown that the alkyne stretching frequency reports quite sensitively on changes in the local environment of the alkyne group, and also that alkyne Raman signals can be detected at orders-of-magnitude lower concentrations than any IR probe groups (including metal carbonyls). We have also discovered that aromatic nitro groups display very strong Raman signals, so strong in fact that they overcome the protein- and media-based background in the same frequency regions.  The similarities and differences between nitro groups and alkynes as site-specific reporters of protein structure will be discussed, including the physical bases for why these signals are so strong. New applications of each group to functional understanding in proteins and/or peptides will also be introduced.

Very strong Raman probe groups report on protein structural changes

2019 Spring National Meeting

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