title: First homo-peptides undergoing a reversible 3(10)-helix/alpha-helix transition: critical main-chain length.
abstract: The difference in length between the more elongated peptide 3(10)-helix and the more compact alpha-helix is about 0.4 A/residue. This property makes the 3(10)-/alpha-helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Calpha-tetrasubstituted alpha-amino acid Calpha-methyl-L-valine, we show that a well defined, solvent controlled, reversible 3(10)-/alpha-helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism.
authors.affiliation: Institute of Biomolecular Chemistry, CNR, Department of Chemistry, University of Padova, 35131 Padova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moretto
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Bernard
authors.initials: B
authors.lastname: Kaptein
authors.forename: Quirinus B
authors.initials: QB
authors.lastname: Broxterman
authors.forename: Ling
authors.initials: L
authors.lastname: Wu
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Keiderling
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D002942:Circular Dichroism; D010455:Peptides / Q000737:chemistry*; D020005:Propanols / Q000737:chemistry; D017433:Protein Structure, Secondary; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D006845:Hydrocarbons, Fluorinated
chemical_list: D010455:Peptides; D020005:Propanols; D012996:Solutions; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated