Vibrational spectroscopy and DFT calculations of di-amino acid peptides: alpha- and beta-N-acetyl-L-Asp-L-Glu in the solid state

Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the di-amino acid peptide derivatives alpha- and beta-N-acetyl-L-Asp-L-Glu have been undertaken. Raman and infrared spectra have been recorded for samples in the solid state. DFT simulations were conducted using the B3-LYP correlation functional and the cc-pVDZ basis set to determine energy minimized/geometry optimized structures (based on a single isolated molecule in the gaseous state). Normal coordinate calculations have provided vibrational assignments for fundamental modes, including their potential energy distributions. Significant differences are observed between alpha- and beta-N-acetyl-L-Asp-L-Glu both in the computed structures and in the vibrational spectra. The combination of experimental and calculated spectra provide an insight into the structural and vibrational spectroscopic properties of di-amino acid peptide derivatives. Copyright (C) 2009 John Wiley & Sons, Ltd.