Düsseldorf 2007 – scientific programme

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MO: Fachverband Molekülphysik

MO 11: Biomolecules

MO 11.7: Talk

Monday, March 19, 2007, 15:30–15:45, 6B

Enantiomeric dependence of the THz spectra of polycrystalline Tyrosine and Valine — •Konstanze Schröck¹, Alan B. True², Timothy A. French², Martina Havenith¹, and Charles A. Schmuttenmaer² — ¹Institute of Physical Chemistry II, Ruhr-University Bochum, Universitatsstr. 150, 44780 Bochum, Germany — ²Yale University, Department of Chemistry, PO Box 208107, 225 Prospect St., New Haven, CT 06520-8107, USA

We used Terahertz Time-Domain Spectroscopy (THz TDS) to investigate the far-infrared absorption features of the two amino acids tyrosine and valine. The THz radiation was generated on a ZnTe(110) crystal by a regeneratively amplified Ti:Sapphire laser (repetition rate of 1 kHz, wavelength of 800 nm, 100 fs pulses with an energy of 1 mJ). The polycrystalline samples were pressed into pellets with a thickness of 0.25-0.5 mm. They were placed in a cryostat and spectra were taken under vacuum at room temperature and at 77 K. Furthermore, a temperature-dependent study of valine in the range of 77 to 290 K was undertaken. The absorption spectra of both the D and L enantiomers, as well as the DL racemates in the range of 0.1 to 2.5 THz will be presented. We show that the vibrational spectra of the D and L enantiomers are identical, but differ from the racemic mixtures. For all samples, the absorption maxima were found to be red-shifted as a function of increasing temperature. Furthermore, a computational study (CHARMM) was used to identify the molecular motions observed in the spectra. The vibrational modes are more intermolecular than intramolecular in character due to the hydrogen-bonding network.