A simple and realistic model system for studying
hydrogen bonds in beta-sheets
Dr Berit Hinnemann
Wydział Fizyki Duńskiego
Uniwersytetu Technicznego w Lyngby
Dania
We investigate the interaction between peptide chains at the level of
state-of-the-art ab initio density functional theory. We propose an
interacting periodic polypeptide model for studying the interactions in
beta-sheets and apply this to glycine and alanine peptide chains in both
parallel and antiparallel structures. The calculated structures of
alanine are compared to x-ray structures of beta-sheets and the model is
found to reproduce the geometry of the hydrogen bonds very well both
concerning parallel and antiparallel beta-sheets. We investigate the
structures of both the N-H...O=C and the C-alpha-H...O=C hydrogen bonds.
The former is thoroughly investigated, whereas the structure of the
latter still is the subject of much discussion. We show that the
hydrogen bonds between peptide chains are considerably weaker than what
is found in studies of smaller models, e.g., the N-methylacetamide
molecule. By molecular mechanics calculations we study the effect of
twisting, which is not included in our model. We estimate its
contribution to the interaction energy to be small.
6.09.2004
