Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 8: Biological Systems
CPP 8.4: Vortrag
Mittwoch, 4. April 2001, 16:45–17:05, 111
Density functional study of hydrogen-bond strength in finite and infinite alpha-helices — •Joel Ireta1, Joerg Neugebauer1, Matthias Scheffler1, Arturo Rojo2 und Marcelo Galvan2 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin Germany — 2Universidad Autonoma Metropolitana-Iztapalapa, D.F. Mexico
The hydrogen-bonds are well known to exhibit cooperative interactions and to play a crucial role in several protein processes, e.g. protein folding. However, due to the complexity of proteins previous studies of hydrogen bonds on these systems focused on isolated molecular structures to extract hb energies thus neglecting the protein backbone. We have therefore studied the energetics of finite and infinite polyalanine chains in the alpha-helical structure employing density-functional theory. The calculations were carried out within the gradient-corrected approximation (PBE functional), and ab initio pseudopotentials with the parallel version of the FHImd code. Based on these results we derive a formalism which allows to extract the energy of hydrogen bonds. Here we focus on two limiting cases: an isolated hydrogen bond and a hydrogen bond within an infinite alpha-helical chain. For the isolated hydrogen bond we find a bond energy of 4kcal/mol (0.17 ev/hb). In the limit of an infinite helix this value is 9kcal/mol (0.39 ev/hb), i.e. the hydrogen bond interaction is strongly cooperative and strengthens each individual bond by more than a factor of two.