title: Conformational properties of hybrid peptides containing alpha- and omega-amino acids.
abstract: This review briefly surveys the conformational properties of guest omega-amino acid residues when incorporated into host alpha-peptide sequences. The results presented focus primarily on the use of beta- and gamma-residues in alphaomega sequences. The insertion of additional methylene groups into peptide backbones enhances the range of accessible conformations, introducing additional torsional variables. A nomenclature system, which permits ready comparisons between alpha-peptides and hybrid sequences, is defined. Crystal structure determination of hybrid peptides, which adopt helical and beta-hairpin conformations permits the characterization of backbone conformational parameters for beta- and gamma-residues inserted into regular alpha-polypeptide structures. Substituted beta- and gamma-residues are more limited in the range of accessible conformation than their unsubstituted counterparts. The achiral beta,beta-disubstituted gamma-amino acid, gabapentin, is an example of a stereochemically constrained residue in which the torsion angles about the Cbeta-Cgamma (theta1) and Calpha-Cbeta (theta2) bonds are restricted to the gauche conformation. Hybrid sequences permit the design of novel hydrogen bonded rings in peptide structures.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: R S
authors.initials: RS
authors.lastname: Roy
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D000596:Amino Acids; D010455:Peptides