Xinyu Liu, Samuel H Gellman

Jul 19, 2021
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Assemblies of racemic β‐sheet‐forming peptides have attracted attention for biomedical applications because racemic forms of peptides can self‐associate more avidly than do single enantiomers. In 1953, Pauling and Corey proposed "rippled β‐sheet" modes of H‐bond‐mediated interstrand assembly for alternating L‐ and D‐peptide strands; this structural hypothesis was complementary to their proposal of "pleated β‐sheet" assembly for L‐peptides. Although no high‐resolution structure has been reported for a rippled β‐sheet, there is strong evidence for the occurrence of rippled β‐sheets in racemic peptide assemblies. Here we compare propensities of peptide diastereomers in aqueous solution to form a minimum increment of β‐sheet in which two antiparallel strands associate. β‐Hairpin folding is observed for homochiral peptides with aligned nonpolar side chains, but no β‐hairpin population can be detected for diastereomers in which one strand contains L residues and the other contains D residues. These observations suggest that rippled β‐sheet assemblies are stabilized by interactions between β‐sheet layers rather than interactions within these layers.
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