Regensburg 2013 – scientific programme
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BP: Fachverband Biologische Physik
BP 14: Biomaterials and Biopolymers I (joint with CPP)
BP 14.8: Talk
Tuesday, March 12, 2013, 11:45–12:00, H34
Structure formation in homologous peptides:
Ac-Ala6-Lys(H+) versus Ac-βAla6-Lys(H+) — •Franziska Schubert, Carsten Baldauf, Mariana Rossi, Volker Blum, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin
β-peptides are non-natural peptides composed of β-amino acid residues that feature one additional methylene group in the backbone compared to natural α-amino acids. Due to their larger flexibility, β-peptides are valuable for the design of new peptides with specific chemical or pharmacological properties. We here investigate the differences in structure formation between α- and β-peptides from first principles employing density-functional theory (DFT) with the PBE functional corrected for van der Waals interactions[1]. We focus this presentation on a comparison of Ac-βAla6-Lys(H+) and Ac-Ala6-Lys(H+) under in vacuo “clean-room” conditions and compare to experimental ion mobility spectrometry[2]. Our conformational search is based on replica exchange molecular dynamics. After generating a large pool of force field-based structures, we relax thousands of conformers with DFT. For the β-peptide, the finite-T vibrational free energy part is essential to recover a conformational hierarchy consistent with experiment. While Ac-Ala6-Lys(H+) is found to be α-helical at 300K, Ac-βAla6-Lys(H+) is seen to vary between 310, α, and π analog helices. Our simulations show that conformational entropy plays a critical role, and an ab initio quantitative assessment is a big challenge that we (and the field) must meet next. [1] A. Tkatchenko, M. Scheffler, PRL 102, 073005 (2009); [2] S. Warnke, K. Pagel, G. von Helden, Fritz-Haber-Institut.