Regensburg 2010 – wissenschaftliches Programm
BP 23.2: Vortrag
Donnerstag, 25. März 2010, 10:30–10:45, H43
(Un)folding of a high-temperature stable polyalanine helix from first principles — •Volker Blum, Mariana Rossi, Alex Tkatchenko, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin
Peptides in vacuo offer a unique, well-defined testbed to match experiments directly against first-principles approaches that predict the intramolecular interactions that govern peptide and protein folding. In this respect, the polyalanine-based peptide Ac-Ala15-LysH+ is particularly interesting, as it is experimentally known to form helices in vacuo, with stable secondary structure up to ≈ 750 K . Room-temperature folding and unfolding timescales are usually not accessible by direct first-principles simulations, but this high T scale allows a rare direct first-principles view. We here use van der Waals corrected  density functional theory in the PBE generalized gradient approximation as implemented in the all-electron code FHI-aims  to show by Born-Oppenheimer ab initio molecular dynamics that Ac-Ala15-LysH+ indeed unfolds rapidly (within a few ps) at T=800 K and 1000 K, but not at 500 K. We show that the structural stability of the α helix at 500 K is critically linked to a correct van der Waals treatment, and that the designed LysH+ ionic termination is essential for the observed helical secondary structure.  M. Kohtani et al., JACS 126, 7420 (2004).  A. Tkatchenko, M. Scheffler, PRL 102, 073005 (2009).  V. Blum et al., Comp. Phys. Comm. 180, 2175 (2009).