Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 24: Biomolecules 2
MO 24.2: Vortrag
Freitag, 21. März 2014, 14:15–14:30, BEBEL SR144
The α-Helix Motif in β-Peptides — Franziska Schubert1, Kevin Pagel1, Mariana Rossi1,2, Stephan Warnke1, Gert von Helden1, Volker Blum1,3, •Carsten Baldauf1, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Physical and Theoretical Chemistry, University of Oxford, U.K. — 3MEMS, Duke University, Durham, U.S.A.
The natural α-helix motif is important in protein-protein recognition and binding. Its imitation by non-natural peptides may open route to modulators of protein interactions. In order to identify the prominent α-helix-motif also in β-peptides, we compare the conformational preferences of peptides Ac-(Xaa)6-LysH+, with Xaa being the α-amino acid alanine (peptide Pα) or its β-equivalent homo-alanine (peptide Pβ) that contains one more methylene unit than the α-building block. Such polyalanine-peptides were developed by Jarrold and co-workers to form α-helices in the gas phase.[1] Conformational space of Pα and Pβ was sampled globally by force field replica-exchange molecular dynamics (REMD) and then refined locally by ab initio REMD with the PBE functional corrected for long-range dispersion. Pα is found to be mostly α-helical in the gas-phase at 300K.[2] Considering harmonic free energy corrections for Pβ, we find helical and non-helical conformers in the low free-energy regime. Helices are strongly stabilized by vibrational free energy. The combination of simulations with vibrational spectra and collision cross sections provides the first evidence for the α-helix motif in β-peptides. [1] Hudgins, Ratner, Jarrold: JACS 120, 12974 (1999); [2] Rossi, Scheffler, Blum: JPCB 117, 5574 (2013).