title: Three-residue turn in β-peptides nucleated by a 12/10 helix.
abstract: A new three-residue turn in β peptides nucleated by a 12/10-mixed helix is presented. In this design, β peptides were derived from the 1:1 alternation of C-linked carbo-β-amino acid ester [BocNH-(R)-β-Caa(r)-OMe] (Boc=tert-butyloxycarbonyl), which consisted of a D-ribo furanoside side chain, and β-hGly residues. The hexapeptide with (R)-β-Caa(r) at the N terminus showed the 'turn' stabilized by a 14-membered NH(4)⋅⋅⋅CO(6) hydrogen bond at the C terminus nucleated by a robust 12/10-mixed helix, thus providing a 'helix-turn' (HT) motif. The turn and the helix were additionally stabilized by intraresidue electrostatic interaction between the furan oxygen in the carbohydrate side chain and NH in the backbone. However, the hexapeptide with a β-hGly residue at the N terminus demonstrated the presence of a 10/12 helix through its entire length, which again showed the intraresidue interaction between NH and furan oxygen. The intraresidue NH⋅⋅⋅O-Me electrostatic interactions observed in the monomer, however, were absent in the peptides.
authors.affiliation: Organic and Biomolecular Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007 (India), Fax: (+91) 40-27160387/27193108. esmvee@iict.res.in.
authors.forename: Gangavaram V M
authors.initials: GV
authors.lastname: Sharma
authors.forename: Thota Anupama
authors.initials: TA
authors.lastname: Yadav
authors.forename: Kanakaraju
authors.initials: K
authors.lastname: Marumudi
authors.forename: Prashanth
authors.initials: P
authors.lastname: Thodupunuri
authors.forename: Pothula Purushotham
authors.initials: PP
authors.lastname: Reddy
authors.forename: Ajit C
authors.initials: AC
authors.lastname: Kunwar
mesh_terms: D002942:Circular Dichroism; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D055672:Static Electricity; D013237:Stereoisomerism
chemical_list: D010455:Peptides
keywords: electrostatic interactions; foldamers; helical structures; hydrogen bonds; peptides