IR-LD spectroscopic characterization of L-Tryptophan containing dipeptides

IR-spectroscopic and stereo-structural analysis of aromatic L-Tryptophan containing dipeptides L-Tryptophan-L-Tryptophan (Trp-Trp), L-Tyrosine-L-Tryptophan (Tyr-Trp) and cyclo(Trp-Trp) have been carried out by means of solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented as suspension in nematic liquid crystal solids. The experimental data have been compared with analogous ones of the simple amino acids L-Tyrosnine (L-Tyr) and L-Tryptophan (L-Trp). In cyclo(Trp-Trp), the IR-spectral changes towards the IR-ones of acyclic Trp-Trp have been determined. A theoretical analysis of Tyr-Trp at Hartree-Fock level of theory and 6-31G** basis set is also applied. (c) 2005 Elsevier B.V. All rights reserved.