The crystal structure of Z‐(Aib)10‐OH at 0.65 Å resolution: three complete turns of 310‐helix |
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Authors: | Renate Gessmann Hans Brückner Kyriacos Petratos |
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Affiliation: | 1. IMBB/FORTH, Iraklion Crete, Greece;2. Department of Food Sciences, Interdisciplinary Research Center, Justus‐Liebig‐University of Giessen, Giessen, Germany |
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Abstract: | The synthetic peptide Z‐(Aib)10‐OH was crystallized from hot methanol by slow evaporation. The crystal used for data collection reflected synchrotron radiation to sub‐atomic resolution, where the bonding electron density becomes visible between the non‐hydrogen atoms. Crystals belong to the centrosymmetric space group P . Both molecules in the asymmetric unit form regular 310‐helices. All residues in each molecule possess the same handedness, which is in contrast to all other crystal structure determined to date of longer Aib‐homopeptides. These other peptides are C‐terminal protected by OtBu or OMe. In these cases, because of the missing ability of the C‐terminal protection group to form a hydrogen bond to the residue i‐3, the sense of the helix is reversed in the last residue. Here, the C‐terminal OH‐groups form hydrogen bonds to the residues i‐3, in part mediated by water molecules. This makes Z‐(Aib)10‐OH an Aib‐homopeptide with three complete 310‐helical turns in spite of the shorter length it has compared with Z‐(Aib)11‐OtBu, the only homopeptide to date with three complete turns. |
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Keywords: | α ‐aminoisobutyric acid 310‐helix sub‐atomic resolution centrosymmetry achiral peptide left‐handed helix unprotected peptide three complete turns |
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