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The first non‐helical Aib‐containing hexapeptide: The crystal structure of Z‐Gly‐Aib‐Gly‐Aib‐Gly‐Aib‐O t Bu

DOI: 10.1002/psc.3307 DOI Help

Authors: Renate Gessmann (IMBB, FORTH) , Hans Brückner (Justus‐Liebig‐University of Giessen) , Kyriacos Petratos (IMBB, FORTH)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Peptide Science , VOL 85

State: Published (Approved)
Published: February 2021

Abstract: The synthetic peptide Z‐Gly‐Aib‐Gly‐Aib‐Gly‐Aib‐OtBu was crystallized from a mixture of ethyl acetate and n‐hexane. The crystals belong to the centrosymmetric space group Pbca. There are three molecules in the asymmetric unit. The three molecules differ mainly in the Z‐group conformation. The first Gly residue adopts a fully extended conformation, residues 2 and 3 lie in the left‐handed helical region, residues 4 and 5 in the right‐handed helical region, and residue 6 again in the left‐handed helical region of the Ramachandran plot. There are only two of four possible intramolecular hydrogen bonds formed, namely, between Aib4 and Gly1 forming a β‐turn of type III′ and between Aib6 and Gly3 forming a β‐turn of type I. The inverted molecules (by space group symmetry) lie in the regions with opposite handedness and form β‐turns of type III and I′. In contrast to all known long synthetic and naturally occurring Aib‐containing peptides that fold as 310‐ or α‐helix, Z‐(Gly‐Aib)3‐OtBu folds in a quite flat structure from which only the protecting groups bulge out.

Journal Keywords: achiral peptide; centrosymmetry; crystal structure; Gly‐Aib peptide; non‐helical Aib‐peptide; α‐aminoisobutyric acid

Subject Areas: Chemistry, Biology and Bio-materials

Instruments: I24-Microfocus Macromolecular Crystallography

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