Stuttgart 2012 – scientific programme

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MO: Fachverband Molekülphysik

MO 11: Biomolecules

MO 11.4: Talk

Tuesday, March 13, 2012, 14:45–15:00, V38.02

IR-MPD and H-/D-exchange studies on aspartame (Asp-Phe-OMe) and Asp-Phe — •Lars Barzen¹, Christine Merkert¹, Fabian Menges¹, Yevgeniy Nosenko¹, Gereon Niedner-Schatteburg¹, Philippe Maitre², and Jean-Michel Ortega² — ¹TU Kaiserslautern, Fachbereich Chemie, Erwin-Schrödinger-Str. 52, 67663 Kaiserslautern, Germany — ²CLIO/LCP, Université Paris-Sud 11, 91405 Orsay Cedex, France

Aspartame (Asp-Phe-OMe), which is a well known sweetener, and its unprotected analog Asp-Phe have been investigated in the gas phase in the form of protonated cations, of deprotonated anions and of alkali metal cation adducts. We recorded infrared multiphoton dissociation (IR-MPD) spectra of protonated and deprotonated aspartame and Asp-Phe in the range of 2200 - 3900 cm⁻¹ by a Laservision IR-OPO system and of protonated and deprotonated aspartame in the range of 600 - 1800 cm⁻¹ through application of the Free Electron Laser (FEL) CLIO in Orsay, Paris. For the protonated and deprotonated species and for the alkali metal ion adducts (Li-Cs) of both peptides the most stable structures and IR-spectra have been calculated at DFT level (B3LYP//cc-pVDZ/Stuttgart RSC 1997) and have been compared with respect to their alkali binding sites. H-/D-exchange studies of the protonated and of the alkali metal attached species (Li-K) with ND₃ in our 7-T-Bruker-FT-ICR mass spectrometer give information on the number of easily accessible / available acidic protons and therefore help to elucidate the structure of these molecules. These results are compared to the calculated minimum structures.