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MO: Fachverband Molekülphysik
MO 16: Biomoleküle
MO 16.8: Poster
Tuesday, March 11, 2008, 14:00–19:00, Poster C1
Mid and Near-Infrared spectra of conformers of H-Pro-Trp-OH and H-Trp-Ser-OH — Kai Seefeld1, •Thomas Häber1, Gernot Engler1, Stefan Grimme2, and Karl Kleinermanns1 — 1Institut für Physikalische Chemie, Heinrich-Heine Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany — 2Theoretische Organische Chemie, Organisch-Chemisches Institut der Universität Münster, Corrensstraße 40, 48149 Münster, Germany
We present near and mid infrared-UV double resonance spectra of the natural di-peptides Pro-Trp and Trp-Ser. In the case of Pro-Trp two conformers are present in the supersonic expansion: a stretched conformer with fully extended backbone and a folded conformer with an OH⋯OCpep hydrogen bond. Both conformers are stabilized by dispersion interaction between indole ring and peptide backbone and a NHpep/Nproline contact. Trp-Ser has two detectable conformers in supersonic expansions. The two conformers both have folded structures where both OH groups are involved in hydrogen bonds. The vibrational and conformational assignment is supported by DFT and ab initio calculations. An adequate description of the energetic order of different conformers requires the explicit inclusion of dispersion. The lowest energy conformers in both systems have peptide backbones that lie on top of the indole ring.