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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Biopolymers (joint session CPP/BP)

CPP 37.1: Talk

Thursday, March 26, 2009, 14:30–14:45, ZEU 114

Secondary structure of polyalanine peptides [Ac-Ala_nLysH⁺ (n=5, 10, 15, 19)] in vacuo – part I (experiment) — •Peter Kupser, Frauke Bierau, Gert von Helden, Mariana Rossi, Volker Blum, Matthias Scheffler, and Gerard Meijer — Fritz-Haber-Institut, D-14195 Berlin, Germany

While vibrational spectroscopy is one of the key techniques to determine the three-dimensional folding arrangements of biological molecules in solution, infrared experiments of gas-phase peptides and proteins can provide information on intrinsic molecular structural properties without interactions with the surrounding solvent molecules [1]. This is also of great interest for theoreticians to test and enhance their models for determining the structure of biomolecules.

Ac-Ala_n-LysH⁺ (n=5, 10, 15, 19) peptides in the gas phase can serve as model systems for a helical secondary structure [2]. Infrared multiphoton dissociation experiments in the regions of the amide I (C=O stretching vibration around 1700 cm⁻¹) and amide II (N-H bending vibration around 1500 cm⁻¹) band on these polyalanine peptides at room temperature were performed using the free electron laser FELIX. The position of the amide I band shifts to lower energies with increasing number of alanines in the chain. Experimental results will be presented and discussed. [1] G. von Helden et al., PCCP 7, 1345 (2005). [2] R. R. Hudgins et al., JACS 120, 12974 (1998).