title: Computational study of conformational preferences of thioamide-containing azaglycine peptides.
abstract: The effect of thioamide substitution on the conformational stability of an azaglycine-containing peptide, For-AzaGly-NH2 (1), was investigated for the sake of finding possible applications by using ab initio and DFT methods. As model compounds, For-[psiCSNH]-AzaGly-NH2 (2), For-AzaGly-[psiCSNH]-NH2 (3), and For-[psiCSNH]-AzaGly-[psiCSNH]-NH2 (4) were used. Two-dimensional phi-psi potential energy surfaces (PESs) for 2-4 were calculated at the B3LYP/6-31G*//HF/6-31G* level in gas (epsilon = 1.0) and in water (epsilon = 78.4) by applying the isodensity polarizable continuum model (IPCM) method. On the basis of these PESs, the minimum energy conformations for 2-4 were characterized at the B3LYP level with 6-31G*, 6-311G**, and 6-31+G** basis sets. The remarkable structural effect of thioamide substitution for 2-4 is that beta-strand structure is observed as a global or local minimum. The minima of 2-4 are also compared with those for glycine and thioamide-containing glycine peptides. Our theoretical results demonstrate that compounds 2-4 would be used to design controllable secondary structures.
authors.affiliation: Department of Chemistry, Korea University, 1 Anam dong, Seoul, 136-701, Korea.
authors.forename: Ho-Jin
authors.initials: HJ
authors.lastname: Lee
authors.forename: Jong Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Jung
authors.forename: Kun-Young
authors.initials: KY
authors.lastname: Kim
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Kim
authors.forename: Young-Sang
authors.initials: YS
authors.lastname: Choi
authors.forename: Chang-Ju
authors.initials: CJ
authors.lastname: Yoon
mesh_terms: D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013816:Thermodynamics; D013854:Thioamides / Q000737:chemistry*
chemical_list: D010455:Peptides; D013854:Thioamides; D005998:Glycine