Intramolecular amide stacking and its competition with hydrogen bonding in a small foldamer.
Attractive interactions between two carboxamide groups in a "stacked" geometry are explored under isolated molecule conditions. Infrared spectra of single conformations of a small gamma-peptide, Ac-gamma(2)-hPhe-NHMe, reveal the presence of a conformation in which the two amide planes are approximately parallel with the amide dipoles in an antialigned orientation. This stacked conformation is energetically comparable to conformations that contain an intramolecular amide-amide H-bond. Amide stacking interactions can compete with H-bonding in circumstances where the amide groups can be brought into a stacking configuration with minimal strain, opening the way for its use in the design of future foldamer structures.
James
William H
WH
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Müller
Christian W
CW
Buchanan
Evan G
EG
Nix
Michael G D
MG
Guo
Li
L
Roskop
Luke
L
Gordon
Mark S
MS
Slipchenko
Lyudmila V
LV
Gellman
Samuel H
SH
Zwier
Timothy S
TS
D000577:Amides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017510:Protein Folding; D055672:Static Electricity; D013816:Thermodynamics
D000577:Amides; D010455:Peptides