Crystal and molecular structure of the doubly unsaturated dehydropeptide Ac-delta Phe-Ala-delta Phe-NH-Me.
The dehydropeptide Ac-delta Phe-L-Ala-delta Phe-NH-Me, containing two dehydro-phenylalanine (delta Phe) 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 delta Phe3, and between the CO of delta Phe1 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 beta-bends. delta Phe1 is located in the (i + 1) position of the first beta-bend, while delta Phe2 is located in the (i + 2) position of the other beta-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.
Ciajolo
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MR
Dipartimento di Chimica, Università di Napoli, Italy.
Tuzi
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A
Pratesi
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CR
Fissi
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A
Pieroni
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O
D000595:Amino Acid Sequence; D003460:Crystallization; D007482:Iothalamate Meglumine; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation
D009842:Oligopeptides; C077026:acetyl dehydrophenylalanyl-alanyl-N-methyldehydrophenylalaninamide; C001694:meglumine ioxithalamate; D007482:Iothalamate Meglumine