Vibrational Analysis of Amino Acids and Short Peptides in Hydrated Media. I. L-glycine and L-leucine

Abstract

Raman scattering and Fourier-transform infrared (FT-IR) attenuated transmission reflectance (ATR) spectra of two alpha-amino acids (alpha-AAs), i.e., glycine and leucine, were measured in H2O and D2O (at neutral pH and pD). This series of observed vibrational data gave us the opportunity to analyze vibrational features of both AAs in hydrated media by density functional theory (DFT) calculations at the B3LYP/6-31++G* level. Harmonic vibrational modes calculated after geometry optimization on the clusters containing each AA and 12 surrounding water molecules, which represent primary models for hydration scheme of amino acids, allowed us to assign the main observed peaks.

The effect of the amphoteric properties of amino acids in the zwitterionic form on the structure of iodine complex compounds in aqueous solutions

“…and their assignments are given in Table 1 Experimental IR-and Raman spectra of an aqueous glycine solution were previously recorded and presented in [19]. In the same study also the first solvation shell for the glycine zwitterion was constructed, and vibrational frequencies calculated using the DFT/B3LYP/6-31++G Ã method.…”

“…For the Ia structure, the vibrational frequencies were computed at the DFT/B3PW9/midi level. Our calculation results and experimental values of vibrational frequencies for the system (a) [19] are shown in Table 2.…”

Vibrational spectroscopy and DFT calculations of amino acid derivatives: N‐acetyl‐L‐Asp and N‐acetyl‐L‐Glu in the solid state

“…It is reported in the literature that the change in the chemical structure of the side-chain affects the geometrical parameters (bond lengths and valence angles) of atoms located in the vicinity of C α . [45] Normal coordinate calculations from DFT computed force constants are critical for assigning the vibrational spectra. In addition, the assignments proposed in the present work have been successfully compared with previous studies on several amino acids and related molecules.…”

Solvent effects on the structures and vibrational features of zwitterionic dipeptides: L-diglycine and L-dialanine

“…The frequencies of the assigned modes derived from the implicit Table 2 Prominent geometrical parameters (valence angles) of L-diglycine (L-G2) and L-dialanine (L-A2) as obtained from the B3LYP/6-31++G(d) geometry optimization for various solvation models Valence angles Tables 3 up to 6. The results derived from these three models are compared with experimental values from Raman and Fourier transform infrared (FT-IR) spectra of L-glycine [9] and L-alanine [10] measured in H 2 O and D 2 O by Ghomi's group. …”

“…The first is present in hight concentrations in muscle and brain tissues, and the second is found in the skeletal muscle and brain of the mammals. L-diglycine (L-Gly-Gly) [3][4][5][6] and L-dialanine(L-Ala-Ala) [6][7][8] are the simplest dipeptides formed respectively with L-glycine [9] and L-alanine [10] amino acids.…”