Conformational preferences of β-sheet structures in cyclopropane-containing γ-peptidesElectronic supplementary information (ESI) available: The geometric parameters and strengths of inter-strand H-bonds in β-sheets of oligo-γ-peptides, and the deformation energies of each strand due to β-sheet formation. See DOI: 10.1039/c5nj00545k

• Main Authors: Lee, Ji Hyang, Park, Hae Sook, Kang, Young Kee
• Format: Journal Article
• Language: English
• Published: 02.06.2015
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c5nj00545k

The conformational preferences of β-sheets in oligo-γ-peptides composed of 2-(aminomethyl)cyclopropanecarboxylic acid (γAmc 3 ) with a cyclopropane constraint on the C α -C β bond were studied using density functional theory (DFT) methods in the gas phase and in solution (chloroform and water). Parallel β-sheets were preferred over the corresponding antiparallel β-sheets in the gas phase. The propensity to form parallel β-sheets increased as the length of the peptide sequence was increased. Parallel β-sheets had larger inter-strand N-H O H-bond energies, whereas antiparallel β-sheets had slightly favored C-H O energies and smaller deformation energies. Thus, the greater stability of parallel β-sheets can be ascribed to the formation of stronger N-H O H-bonds. Antiparallel β-sheets exhibited more favored solvation free energies than did the corresponding parallel β-sheets. Although parallel β-sheets were more stable than antiparallel β-sheets in chloroform, parallel and antiparallel β-sheets exhibited nearly similar stabilities for the tetrapeptide and hexapeptide in water. The greater importance of desolvation in parallel β-sheets compared with antiparallel β-sheets may be partially attributable to the formation of stronger inter-strand N-H O H-bonds in parallel β-sheets. DFT calculations supported the formation of parallel β-sheets for the tetrapeptide and hexapeptide in chloroform, consistent with experimental data for γAmc 3 -containing peptides that form parallel β-sheets in CDCl 3 . The conformational preferences of β-sheets determined here will provide useful information for understanding the conformational preferences of other oligo-γ-peptides with specific functions. Oligo-γ-peptides based on 2-(aminomethyl)cyclopropanecarboxylic acid (γAmc 3 ) with a cyclopropane constraint on the C α -C β bond preferentially formed parallel β-sheets rather than antiparallel β-sheets due to the stronger N-H O H-bonds in the parallel conformation.