Structural versatility of peptides containing C alpha, alpha-dialkylated glycines. An X-ray diffraction study of six 1-aminocyclopropane-1-carboxylic acid rich peptides.
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.
Benedetti
E
E
Department of Chemistry, University of Naples, Italy.
Di Blasio
B
B
Pavone
V
V
Pedone
C
C
Santini
A
A
Barone
V
V
Fraternali
F
F
Lelj
F
F
Bavoso
A
A
Crisma
M
M
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
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D009842:Oligopeptides; C023863:1-aminocyclopropane-1-carboxylic acid; D005998:Glycine