Regensburg 2002 – scientific programme
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SYBM: Physik biologischer Materie
SYBM 302: Biomolecular mechanics
SYBM 302.2: Talk
Tuesday, March 12, 2002, 17:15–17:30, H37
Hydrogen-bond bifurcation in an α-helix under uniaxial strain: a DFT study — •Joel Ireta1, Jörg Neugebauer1, Matthias Scheffler1, Arturo Rojo2, and Marcelo Galván2 — 1Fritz-Haber-Institut der MPG, Berlin — 2Universidad Autónoma Metropolitana-Iztapalapa, México D.F., México
New experimental techniques allow to stretch or compress proteins such that unfolding can be induced by breaking inter chain or intra chain non-covalent bonds. Studying the response of polypeptides (short fragments of proteins) to such mechanical deformations may provide detailed insight into the stability and biological activity of proteins. We used density functional theory (GGA-PBE) to study the mechanical response of an infinite polyalanine chain in α-helical conformation. We thereto calculated the NH⋯O hydrogen-bond (hb) energy as well as the strain energy of a peptide unit as function of uniaxial strain along the helix axis. Our results show that if the uniaxial pressure exceeds 2 GPa the strain energy exceeds the NH⋯O hb energy: the helix becomes unstable (denatured). A detailed analysis of the rotational barriers of the methyl groups showed that at high strain a new type of hbs are formed (CH⋯O), i.e., the hbs show bifurcation. The presence of these new type of hbs at high strain reduces the energy of the NH⋯O hbs by about 2-3 kcal/mol, thus the helix becomes denaturated at lower compression.