Regensburg 2004 – scientific programme
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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 3.18: Poster
Wednesday, March 10, 2004, 16:00–18:30, B
Density functional theory study of alpha-helical polypeptides under tensile strain — •Joel Ireta1, Jörg Neugebauer1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin — 2Theoretische Physik, Universität Padeborn
Recent experimental techniques employing e. g. optical tweezers or atomic force microscopes make it possible to monitor the behavior of biopolymers under tensile strain. Using this technique force-driven phase transitions occurring at single molecule level have been observed. While such studies give important information they are (presently) not able to provide insight into the atomistic details of such processes. We have therefore studied the mechanical response of infinite polyalanine and polyglicine chains in alpha-helical conformation since these structures represent the smallest but still realistic models of a protein. We employ density functional theory, ab initio pseudopotentials and the Perdew-Burke-Ernzerhof formulation for the exchange and correlation functional. Calculating the response force along the helix axis as function of strain, we have identified a plateau region at forces of about 25 pN. The presence of a plateau is characteristic for a first order phase transition. An analysis of the helical structures shows that sizeable changes in the covalent bonds of the peptide unit (particularly carbon and nitrogen pyramidalization) are the driving force causing the phase transition.