Conformational analysis of TOAC-labelled alamethicin F50/5 analogues |
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Authors: | Peggion Cristina Jost Micha De Borggraeve Wim M Crisma Marco Formaggio Fernando Toniolo Claudio |
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Affiliation: | Institute of Biomolecular Chemistry, Padova Unit, CNR, Department of Chemistry, University of Padova, Padova. |
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Abstract: | In the preceding paper in this issue, we reported the total syntheses in solution of a set of four TOAC-containing analogues of the [L-Glu(OMe)(7,18,19)] F50/5 component of alamethicin, the prototype of peptaibol antibiotics forming channels in the biological membranes. In this article, we have expanded this work to the examination of their preferred conformation in solution by use of a combination of CD, FT-IR absorption, and NMR spectroscopies. The results are strongly in favor of the view that replacement of the Aib residues at positions 1, 8, and 16 with TOAC (both are members of the helicogenic sub-class of C(alpha)-tetrasubstituted alpha-amino acids) does not significantly affect the overwhelmingly populated alpha-helical 3D structure of alamethicin. The X-ray diffraction crystal structure of the N(alpha)-protected, C-terminal, hexapeptide amide segment Z-L-Pro-L-Val-(Aib)(2)-[L-Glu(OMe)](2)-Fol lends further support to our conformational conclusions. |
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Keywords: | Peptaibols Alamethicin F50/5 analogs Nitroxide peptides Conformational analysis CD Spectroscopy NMR Spectroscopy IR Spectroscopy X‐Ray crystallography |
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