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Crystal and molecular structure of Boc‐ D ‐Ala‐ΔPhe‐Gly‐ΔPhe‐ D ‐Ala‐OMe: A 3 10 ‐helical dehydropeptide
Author(s) -
Ciajolo M. Rosaria,
Tuzi Angela,
Pratesi Claudio R.,
Fissi Adriano,
Pieroni Osvaldo
Publication year - 1990
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.360300906
Subject(s) - chemistry , pentapeptide repeat , crystallography , hydrogen bond , molecule , crystal structure , stereochemistry , peptide , turn (biochemistry) , alanine , amino acid , biochemistry , organic chemistry
The crystal and molecular structure of the pentapeptide Boc‐ D ‐Ala‐ΔPhe‐Gly‐ΔPhe‐ D ‐Ala‐OMe, containing two dehydrophenylalanine residues, was determined by x‐ray diffraction. The molecule crystallizes in the orthorombic P2 1 2 1 2 1 space group, with a = 10.439(3), b = 15.319(3) and c = 21.099(4) Å. In the solid state, the conformation of the pentapeptide is characterized by the presence of two type III′ β‐turns. Thus the peptide assumes a left‐handed 3 10 ‐helical conformation, the left sense being due to the D configuration of the alanine residues. The two unsaturated residues are located in the ( i + 1) position of the first β‐turn and in the ( i + 2) position of the second β‐turn, respectively. In the crystal, the helical molecules are linked head to tail by hydrogen bonds. Lateral hydrogen bonds are also formed between molecules related by a twofold screw symmetry. This gives rise to a typical mode of packing characterized by infinite helical “chains,” smiliar to the packing found in other oligopeptides that adopt a 3 10 ‐helical structure.