title: Analysis of N-amino-imidazolin-2-one peptide turn mimic 4-position substituent effects on conformation by X-ray crystallography.
abstract: N-Amino-imidazolin-2-ones, a new class of turn mimics onto which side chains of different amino acids may be added conveniently, have been analyzed by X-ray crystallography. 4-Methyl and 4-benzyl N-amino-imidazolin-2-one tetrapeptide models 2 and 3 were examined to study the influence of the 4-position substituent on turn conformation and the chi dihedral angle of the neighbouring C-terminal residue side-chain. The nature of the 4-position substituent caused substantial effects on the ψ(i + 2) main chain and C-terminal Phe χ(1) side-chain dihedral angle values, giving a preference for β- and γ-turn conformers for the methyl- and benzyl-substituted imidazolin-2-ones, respectively. Conformational analysis in the solid state has provided insight to guide application of N-amino-imidazolin-2-ones in peptide mimicry.
authors.affiliation: Département de Chimie, Université de Montréal, C.P. 6128, Succursale Center-Ville, Montréal, QC H3C 3J7, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Proulx
authors.forename: William D
authors.initials: WD
authors.lastname: Lubell
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D007093:Imidazoles; D010455:Peptides
keywords: beta turns; gamma turns; imidazolin-2-ones; peptide mimicry