Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 200: Poster Session II
AKB 200.18: Poster
Dienstag, 8. März 2005, 17:00–19:00, Poster TU C
Density Functional Theory Study on the Stability of left-handed alpha-Helix Polyalanine — •Franziska Grzegorzewski, Lars Ismer, Joel Ireta, and Matthias Scheffler — Fritz Haber-Institut der Max Planck-Gesellschaft, Faradayweg 4-6, 14193 Berlin
The left-handed α-helix, αL, is an unusual conformation in proteins and, if observed, mainly built with glycine, a non-chiral amino acid. The discrimination of αL-helix has been attributed to unfavorable repulsive interactions between the side chain and the backbone atoms (steric effect). In order to provide a deeper insight on the factors influencing the relative stability of αL-helix we performed systematic ab-initio calculations for polyalanine in different left-handed helical conformations using density functional theory (DFT) in the PBE approximation to the exchange-correlation functional. The potential energy surface of the left-handed polyalanine was explored for numerous configurations using different helix twists and varying the increment along the helix axis per residue. We find three minima corresponding to πL-, αL-, and 310L-helix. Based on an harmonic vibrational analysis, we find that only considering the loss of vibrational entropy in addition to the steric effect, DFT-PBE predicts that a fully extended structure will not fold spontaneously into αL-helix in vacuum at room temperature