Chemistry

Pinning Down β Helices

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Science  11 Aug 2006:
Vol. 313, Issue 5788, pp. 737
DOI: 10.1126/science.313.5788.737a

The β-helical motif, which is formed by alternating D and L amino acids, has been pursued less often in small-peptide design than the more familiar α and 310 helices, in part because the peptide can remain single-stranded or produce a mixture of parallel and antiparallel forms. Sastry et al. have designed and chemically synthesized β hairpin/β helix cyclic peptides with 5.6 residues per turn that form antiparallel helices in organic solvent. In the two peptides, two strands of either Val or Leu residues of alternating handedness are joined by two Pro-Gly hairpins and stabilized by 16 hydrogen bonds; circular dichroism spectroscopy confirmed that the sequences chosen create a left-handed Leu helix and a right-handed Val helix. Analysis of nuclear magnetic resonance spectra and amide vibrations in the infrared absorption spectrum indicated that the antiparallel helices are quite stable in solution, but that a variant with only one β hairpin exists in multiple conformations. The authors suggest that derivatives with more hydrophilic amino acids should exhibit similar stability in aqueous media. — PDS

J. Am. Chem. Soc. 128, 10.1021/ja062737f (2006).

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