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

• Published in: Journal of Raman spectroscopy 2009-06, Vol.40 (6), p.661-669
• Main Authors: Kausar, Nighat, Alexander, Bruce D., Dines, Trevor J., Withnall, Robert, Chowdhry, Babur Z.
• Format: Article
• Language: English
• Subjects: cis/trans conformation; DFT calculations; FT-IR spectroscopy; Raman spectroscopy; spectral assignments; α- and β-N-acetyl-Asp-L-Glu
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.2179

Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the di‐amino acid peptide derivatives α‐ and β‐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 α‐ and β‐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 © 2009 John Wiley & Sons, Ltd. Significant differences in the experimental (Raman/FT‐IR) and calculated spectra (DFT: B3‐LYP/cc‐pVDZ) of an α‐neuropeptide and its biologically inactive β‐ analog are reported.