title: Structural versatility of peptides containing C alpha, alpha-dialkylated glycines. An X-ray diffraction study of six 1-aminocyclopropane-1-carboxylic acid rich peptides.
abstract: The molecular and crystal structures of six fully blocked, Ac3c-rich peptides to the tetramer level were determined by X-ray diffraction. The peptides are Fmoc-(Ac3c)2-OMe-CH3OH, Ac-(Ac3c)2-OMe, t-Boc-Ac3c-L-Phe-OMe, pBrBz-(Ac3c)3-OMe.H2O, Z-Gly-Ac3c-Gly-OTmb.(CH3)2CO, and t-Boc-(Ac3c)4-OMe.2H2O. Type-I (I') beta-bends and distorted 3(10)-helices were found to be typical of the tri- and tetrapeptides, respectively. In the dipeptides, too short to form beta-bend conformations, other less common structural features may be observed. The average geometry of the cyclopropyl moiety of the Ac3c residue is asymmetric and the N-C alpha-C' bond angle is significantly expanded from the regular tetrahedral value. A comparison with the structural preferences of other extensively investigated C alpha, alpha-dialylated alpha-amino acids is made and the implications for the use of the Ac3c residue in conformational design are examined.
authors.affiliation: Department of Chemistry, University of Naples, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Benedetti
authors.forename: B
authors.initials: B
authors.lastname: Di Blasio
authors.forename: V
authors.initials: V
authors.lastname: Pavone
authors.forename: C
authors.initials: C
authors.lastname: Pedone
authors.forename: A
authors.initials: A
authors.lastname: Santini
authors.forename: V
authors.initials: V
authors.lastname: Barone
authors.forename: F
authors.initials: F
authors.lastname: Fraternali
authors.forename: F
authors.initials: F
authors.lastname: Lelj
authors.forename: A
authors.initials: A
authors.lastname: Bavoso
authors.forename: M
authors.initials: M
authors.lastname: Crisma
mesh_terms: D000478:Alkylation; D000596:Amino Acids / Q000737:chemistry*; D000598:Amino Acids, Cyclic; D003460:Crystallization; D005998:Glycine / Q000737:chemistry*; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D000598:Amino Acids, Cyclic; D009842:Oligopeptides; C023863:1-aminocyclopropane-1-carboxylic acid; D005998:Glycine