A Stack of Amides

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Science  30 Oct 2009:
Vol. 326, Issue 5953, pp. 645
DOI: 10.1126/science.326_645a

Amides are well arranged to form hydrogen bonds with one another, an interaction that plays a major role in the three-dimensional organization of proteins as well as synthetic supramolecular assemblies. James III et al. have discovered that in the case of γ-peptides, a competing and comparably strong organizing force arises from the amide moiety's substantial dipole. Specifically, they probe small test substrates bearing two amide groups using highly sensitive ultraviolet-infrared double resonance spectroscopy in the gas phase. By comparing the data with simulations, they uncover a conformation in which the planar amides at either end of the molecule stack against one another in antiparallel fashion, so their dipoles adopt a mutually attractive orientation. The authors anticipate that the stacking tendency could prove a useful design element in construction of synthetic foldamers.

J. Am. Chem. Soc. 131, 14243 (2009).

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