Conformational Properties of α-Amino Acids Disubstituted at the α-Carbon

Abstract

The conformational preferences of dipeptides from α-aminoisobutyric acid (Aib), 1-aminocyclopropane-1-carboxylic acid (Ac3c), and 1-aminocyclobutane-1-carboxylic acid (Ac4c) residues have been determined by ab initio quantum mechanical calculations. The results obtained evidence for the intrinsic helix-forming tendency of the Aib residue. Furthermore, the conformational preferences of Ac3c and Ac4c dipeptides are reported and the differences explained in terms of the size of their cyclic side chains. Finally, the large number of minima characterized for these conformationally restricted residues is explained as a function of the deformability of the molecular geometries.

Protein Segments with Conformationally Restricted Amino Acids Can Control Supramolecular Organization at the Nanoscale

“…Among the Ac n c series, the intrinsic conformational propensities of the cyclopropane (Ac 3 c), cyclobutane (Ac 4 c), cyclopentane (Ac 5 c), and cyclohexane (Ac 6 c) members (Figure 1) have been extensively investigated. [11][12][13][16][17][18][19][20][21] Results indicated that the preferences of these amino acids strictly parallel those of Aib, i.e. they induce folded structures in the 3 10 -/ R-helix region ( ,Ψ ≈ (60°, (30°), with some distortion in the case of Ac 3 c, which prefers the spatially close bridge region ( ,Ψ ≈ (80°, (0°).…”

Analysis of the conformational profile of trishomocubane amino acid dipeptide

“…The conformational space of Ac-Tris-NHMe was compared with our previous results, 15,16 including Ac-PCU-NHMe, Ac-Ala-NHMe, Ac-Gly-NHMe, and Ac-Aib-NHMe (see Supplementary Material). Glycine tends to favor extended conformations and alanine exhibit some helical conformations, while the conformations of aminoisobutyric acid 16,[32][33][34] are very similar to that exhibited by Ac-Tris-NHMe. Interestingly, the intramolecular hydrogen bond predicted for the C 7 conformation of the Aib dipeptide (H. .…”

Antimicrobial Electrospun Fibers of Polyester Loaded with Engineered Cyclic Gramicidin Analogues

“…More specifically, in such two engineered peptides, the D-Phe was replaced by D-Pro while the L-Pro was changed by two conformationally restrained residues. In the first peptide, hereafter denoted GA-S1 (with sequence cyclo(Val-Orn-Leu-D-Pro-Ac3c)2), L-Pro was replaced by 1-aminocyclopropanecarboxylic acid (Ac3c in Scheme 1), an α,α-dialkylated amino acid with strong stereochemical constraints [40,41]. The second peptide (with sequence cyclo(Val-OrnLeu-D-Pro-S,S-c3diPhe)2), hereafter denoted GA-S2, was designed using an Ac3c derivative with two vicinal phenyl substituents in a trans relative disposition (S,S-c3diPhe in Scheme 1) to replace L-Pro.…”