Berlin 2012 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
BP: Fachverband Biologische Physik
BP 7: Posters: Proteins
BP 7.1: Poster
Montag, 26. März 2012, 17:30–19:30, Poster A
Conformational energy hierarchy of benchmark polyalanine based peptides with secondary structure — •Sucismita Chutia, Mariana Rossi, Volker Blum, and Matthias Scheffler — Fritz-Haber Institute, Berlin, Germany
An important challenge for the theoretical study of peptides and proteins is a faithful representation of the most stable conformations and their energy hierarchy. We here address the accuracy of a first-principles based conformational search approach for two polyalanine-based peptides that are well studied in vacuum experiments and can thus be considered “benchmark cases”. We use a force-field based prescreening of the astronomically large number of possible conformers, followed by thousands of post-relaxations using density functional theory (PBE) with corrections for van der Waals terms [1]. This approach yields good agreement with experiment for the polyalanine based peptide Ac-Ala5-LysH+ [2]. However, in the case of the equally well studied peptide Ac-Phe-Ala5-LysH+ [3], the experimentally observed structures at low temperature are not simply the lowest (potential) energy ones. By varying the density functional, we show that its accuracy could partially account for the discrepancy, but in addition, much better agreement with experiment would result by including room-temperature vibrational free energy contributions. We suggest that the predominance of the experimental conformers is affected by selection/freezing at room temperature. [1] A.Tkatchenko and M.Scheffler, PRL 102, 073005 (2009). [2] M. Rossi et al., J. Phys. Chem. Lett. 1, 3465 (2010). [3] J.A. Stearns et al., PCCP 11, 125 (2009).