Hannover 2013 – scientific programme
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MO: Fachverband Molekülphysik
MO 22: Biomolecules
MO 22.4: Talk
Thursday, March 21, 2013, 11:45–12:00, F 107
Structural investigations on isolated alanine containing peptides with FT-IR spectroscopy in combination with DFT calculations — •Manuel Zimmer, Sebastian Kruppa, and Markus Gerhards — TU Kaiserslautern, Fachbereich Chemie Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern
Due to the direct correlation between structure and functionality of biomolecules the structural investigation of proteins and peptides as well as their amino acid building blocks are of great scientific interest. IR spectroscopy combined with theoretical calculations provides a powerful tool to determine structural preferences of biologically relevant molecules. Thus, this strategy was applied to the protected alanine peptides Ac-Alan-OMe (n=1-4). For comparison with IR spectra recorded in a heatable gas cell possible isomers of the different alanine peptides as well as their IR modes were calculated by DFT and DFT-D3 calculations (B3LYP/TZVP). The application of Grimme dispersion corrections to a stepwise elongated alanine chain allows a systematic investigation of the dispersion influence on the peptide structures. For increasing peptide chain lengths folded structures are energetically favored. This is much more pronounced in calculations including dispersion corrections. It is also observed that dispersion corrections show significantly different results at a chain length of n ≥ 3. From comparison of calculated with experimental IR frequencies it can be deduced that stretched and folded structures can coexist in the gas phase.