10.1021/ja800355p.s007
Soo Hyuk Choi
Soo Hyuk
Choi
Ilia A. Guzei
Ilia A.
Guzei
Lara C. Spencer
Lara C.
Spencer
Samuel H. Gellman
Samuel H.
Gellman
Crystallographic Characterization of Helical Secondary Structures in α/β-Peptides with 1:1 Residue Alternation
American Chemical Society
2008
helix
residue
NMR data
14 crystal structures
backbone amide groups
ACPC
peptide
hydrogen bonds
2008-05-21 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Crystallographic_Characterization_of_Helical_Secondary_Structures_in_Peptides_with_1_1_Residue_Alternation/2937889
Oligomers that contain both α- and β-amino acid residues in a 1:1 alternating pattern have recently been shown by several groups to adopt helical secondary structures in solution. The β-residue substitution pattern has a profound effect on the type of helix formed and the stability of the helical conformation. On the basis of two-dimensional NMR data, we have previously proposed that β-residues with a five-membered ring constraint promote two different types of α/β-peptide helix. The “11-helix” contains <i>i</i>,<i>i</i>+3 CO···H−N hydrogen bonds between backbone amide groups; these hydrogen bonds occur in 11-atom rings. The α/β-peptide “14/15-helix” contains <i>i</i>,<i>i</i>+4 CO···H−N hydrogen bonds, which occur in alternating 14- and 15-atom rings. Here we provide crystallographic data for 14 α/β-peptides that form the 11-helix and/or the 14/15-helix. These results were obtained for a series of oligomers containing β-residues derived from (<i>S,S</i>)-<i>trans</i>-2-aminocyclopentanecarboxylic acid (ACPC) and α-residues derived from α-aminoisobutyric acid (Aib) or l-alanine (Ala). The crystallized α/β-peptides range in length from 4 to 10 residues. Nine of the α/β-peptides display the 11-helix in the solid state, three display the 14/15-helix, and two display conformations that contain both <i>i</i>,<i>i</i>+3 and <i>i</i>,<i>i</i>+4 CO···H−N hydrogen bonds, but not bifurcated hydrogen bonds. Only 3 of the 14 crystal structures presented here have been previously described. These results suggest that longer α/β-peptides prefer the 14/15-helix over the 11-helix, a conclusion that is consistent with previously reported NMR data obtained in solution.