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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology

SYLS 3: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"

SYLS 3.29: Poster

Mittwoch, 10. März 2004, 16:00–18:30, B

Density-Functional Study of Left handed Helices — •Franziska Grzegorzewski, Joel Ireta, and Matthias Scheffler — Fritz-Haber-Institut Berlin

Knowledge of the factors influencing the stability of protein structures is crucial to understand their biological function and the regulatory mechanisms that enable the protein to adapt to changing conditions in cells. The most ubiquitous conformation in globular proteins is the right-handed α-helix. Considering the polypeptide backbone alone, each helix has an energetically equivalent mirror image. However, left-handed helices seldomly appear in protein structures. The common explanation is that side groups disfavor the left-handed enantiomer. In order to gain a deeper understanding of how the handedness affects the helical stability we performed a density functional theory study on the behavior of infinite polyalanine in a left-, right-handed 310- helical conformation and fully extended structure as a reference system. The study was carried out exploiting periodic boundary conditions and ab initio pseudopotentials, together with the generalized gradient approximation of the exchange-correlation energy functional. A vibrational analysis of the studied structures shows that vibrational entropic contributions are of the same order of magnitude as the side group effect for the destabilization of the left-handed conformation.