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Crystal and molecular structure of the doubly unsaturated dehydropeptide Ac‐ΔPhe‐Ala‐ΔPhe‐NH‐Me
Author(s) -
Ciajolo M. Rosaria,
Tuzi Angela,
Pratesi Claudio R.,
Fissi Adriano,
Pieroni Osvaldo
Publication year - 1992
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360320702
Subject(s) - chemistry , hydrogen bond , intramolecular force , crystallography , antiparallel (mathematics) , intermolecular force , crystal structure , molecule , stereochemistry , physics , organic chemistry , quantum mechanics , magnetic field
The dehydropeptide Ac‐ΔPhe‐L‐Ala‐ΔPhe‐NH‐Me, containing two dehydro‐phenylalanine (ΔPhe) residues, crystallizes from methanol/water in space group P2 1 2 1 2 1 , with a = 12.508 (2), b = 12.746(1) and c = 15.465(9). In the crystalline state, the peptide chain assumes a right‐handed 3 10 ‐helical conformation stabilized by two intramolecular hydrogen bonds, between the N‐terminal acetyl group and the NH of ΔPhe 3 , and between the CO of ΔPhe 1 and the NH of the C‐terminal methylamide group, respectively. The two consecutive 10‐membered rings formed by the hydrogen bonds have torsion angles quite close to the standard values for type III β‐bends. ΔPhe 1 is located in the ( i + 1) position of the first β‐bend, while ΔPhe 2 is located in the ( i + 2) position of the other β‐bend. In the crystal, the molecules are linked head to tail by intermolecular hydrogen bonds to form long helical chains. The axes of the helices are parallel to the c axis, but neighboring helices run in antiparallel directions. This crystal packing is similar to the packing motifs frequently observed in Aib‐containing peptides.