title: Synthesis and preliminary conformational analysis of TOAC spin-labeled analogues of the medium-length peptaibiotic tylopeptin B.
abstract: A set of analogues of the 14-residue peptaibol tylopeptin B, containing the stable free-radical 4-amino-1-oxyl-2,2,6,6,-tetramethylpiperidine-4-carboxylic acid (TOAC) at one or two selected positions, was synthesized by the solid-phase methodology. A solution conformational analysis performed by FTIR absorption and CD suggests that, in membrane-mimicking solvents, the labeled tylopeptin B analogues preserve the helical propensity of the parent peptide, with a preference for the α-helix or the 3(10) -helix type depending upon the nature of the solvent. In aqueous environment, the spin-labeled analogues present a higher content of helical conformation as a consequence of the strong helix promoter effect of the conformationally constrained TOAC residue. We observed a progressive increase of the quenching effect of the nitroxyl radical on the fluorescence of the N-terminal tryptophan as TOAC replaces the Aib residue at positions 13, 8, and 4, respectively. A membrane permeabilization assay performed on two selected analogues, TOAC(8) - and TOAC(13) -tylopeptin B, showed that the labeled peptides exhibit membrane-modifying properties comparable with those of the natural peptaibiotic. We conclude that our TOAC paramagnetic analogues of tylopeptin B are good models for a detailed ESR investigation of the mechanism of membrane permeabilization induced by medium-length peptaibiotics.
authors: ICB-Padova Unit, CNR, Department of Chemical Sciences, University of Padova, 35131, Padova, Italy. marina.gobbo@unipd.it
authors: Marina
authors: M
authors: Gobbo
authors: Elisabetta
authors: E
authors: Merli
authors: Barbara
authors: B
authors: Biondi
authors: Simona
authors: S
authors: Oancea
authors: Antonio
authors: A
authors: Toffoletti
authors: Fernando
authors: F
authors: Formaggio
authors: Claudio
authors: C
authors: Toniolo
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000138:chemical synthesis* / Q000378:metabolism; D002463:Cell Membrane Permeability; D002942:Circular Dichroism; D003497:Cyclic N-Oxides / Q000032:analysis / Q000138:chemical synthesis*; D004578:Electron Spin Resonance Spectroscopy; D005453:Fluorescence; D005609:Free Radicals / Q000138:chemical synthesis / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D054848:Peptaibols; D010455:Peptides / Q000138:chemical synthesis* / Q000378:metabolism; D017433:Protein Structure, Secondary; D060327:Solid-Phase Synthesis Techniques / Q000379:methods*; D012996:Solutions; D012997:Solvents / Q000737:chemistry / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013113:Spin Labels / Q000138:chemical synthesis*; D013194:Staining and Labeling / Q000379:methods*; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D003497:Cyclic N-Oxides; D005609:Free Radicals; D008081:Liposomes; D054848:Peptaibols; D010455:Peptides; D012996:Solutions; D012997:Solvents; D013113:Spin Labels; C403871:tylopeptin B; D014364:Tryptophan; C037109:2,2,6,6-tetramethylpiperidine-N-oxide-4-amino-4-carboxylic acid