Dresden 2003 – wissenschaftliches Programm

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SYCN: Computational nanoscience - from materials to biology

SYCN 102: Computational Nanoscience: From Materials to Biology (Poster, gemeinsam mit SYSE)

SYCN 102.4: Poster

Dienstag, 25. März 2003, 19:00–21:00, ZEU/160

Mechanical response of the alpha-helix secondary structure under tensile and compressive load: DFT study — •Joel Ireta, Joerg Neugebauer, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

Proteins undergo constant motions and structural changes in cells under normal physiological conditions. Therefore, the knowledge of their mechanical properties is necessary to understand their biological function. In order to gain a deeper understanding of how strain affects the atomic geometry, electronic structure, and elastic properties of proteins, we performed a PBE density functional theory study on the behavior of polyalanine and polyglycine in alpha-helical conformation under compressive and tensile load. Assuming a value of 2 angstroms as thickness for the excluded region around the helix, we find a longitudinal Young modulus of 25 GP for polyalanine which agrees well with the reported experimental value of 23.1 GPa. Also we observe that the lateral chain of the aminoacid significantly affects the mechanical response: for example, going from polyglycine to polyalanine compressive load stiffens the system and increases the Young modulus. Further we find that anharmonic contributions under tension are stronger than under compression, and that at high load (strain > 8 percent) elastic instabilities appear.