Berlin 2012 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 7: Posters: Proteins
BP 7.7: Poster
Montag, 26. März 2012, 17:30–19:30, Poster A
How cations change peptide conformation: First principles simulations and infrared spectroscopy — •Carsten Baldauf1, Kevin Pagel1, Volker Blum1, Stephan Warnke1, Gert von Helden1, Beate Koksch2, Gerard Meijer1, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin — 2Institut für Chemie und Biochemie, FU Berlin
Turns are the hinges arranging periodic secondary structure elements (helices and strands) to form compact protein tertiary folds. Li+ alters protein backbone conformation. We investigate this effect on structure and dynamics of turns Ac-Ala-{Ala,Asp}-Pro-Ala-NMe by theoretical conformational analyses and experimental vibrational spectroscopy. As standard force fields apparently lack accuracy for ion-peptide interactions, we demonstrate a trustworthy description of the potential-energy surface of these systems by van der Waals corrected density-functional theory (PBE+vdW) and compare to gas-phase infrared spectroscopy, both approaches in the exact-same clean-room environment. We predict canonical turn conformations for the peptides alone. Li+ and Na+ adsorb to C=O groups, induce unusual backbone conformations, and prevent H bond formation. By including free-energy contributions, essential for consistent theory-experiment comparison, we show that multiple conformers coexist at room temperature. First-principles molecular dynamics simulations lead to theoretical spectra (including anharmonic effects) which indicate low-energy conformers do not equally contribute to the experimental spectra. They also give insights into backbone motion patterns (peptide bond crankshaft rotation).