Experimental and Computational Vibration Study of Amino Acids

Abstract

Vibrational studies of amino acids experimentally and theoretically have been performed. The Semi-empirical methods optimization by PM6 and RM1 on the l-and d-amino acids (alanine, phenylalanine, aspartic and glutamic acid), showed no difference in energy between l-and d-isomers. The vibrational frequencies were calculated by semi-emprical methods (PM6 and RM1) and ab initio methods (B3LYP/6-31+G(d) and were scaled down by factors of 0.925 (RM1), 1.09 (PM6) and 0.89 (B3LYP/6-31+G(d)). The calculated and experimental vibrational frequencies have shown good general agreement.

Biogenic Selenium Nanoparticles: A Fine Characterization to Unveil Their Thermodynamic Stability

“…Consequently to these observations, a putative assignment of the highly convoluted IR signals in the fingerprint region (900–250 cm −1 ) ( Figure 3 ) was proposed based on DFT calculations performed on Se 8 units interacting with L-cysteine and its derivatives ( Figure S1 ; Tables S1 and S2 ). Indeed, although some of the detected contributions were attributed to amino acid residues, fatty acid chains, nucleic acids, alkyl halides, and carboxylic acids [ 68 , 70 ] ( Tables S3 and S4 ), their complete identification solely based on the available literature was often impaired, due to the specificity of the fingerprint region itself. As a result, ATR-FTIR spectra of Micrococcus sp.…”

Zinc Oxide Nanocomposites—Extracellular Synthesis, Physicochemical Characterization and Antibacterial Potential

“…In the ZnO NC FT-IR spectra, a signal at υ = 1400 cm −1 (2) was observed—it is correlated with the plane bending of methylene (−CH 2 ) in the cysteine (Cys) or glycine amino acids [ 48 , 49 ]. In the range of 1100–1200 cm −1 (3), there is an area of C-C stretching: C-H and N-H bending vibrations are typical for amide III [ 44 , 46 , 50 , 51 ] but also for lactic acid and its metabolites [ 52 ]. Additionally, the signal at υ = 800–900 cm −1 (4) is related to the C-H vibrations of bioactive compounds included in the organic deposit on the ZnO NC surface (such as peptides or lipids) [ 10 , 47 , 52 ].…”

Multiple surface interaction mechanisms direct the anchoring, co-aggregation and formation of dual-species biofilm between Candida albicans and Helicobacter pylori

“…Signals c1 and h1 were associated to Amide B vibration which is the result of Fermi resonance between the first overtone of Amide II and the N-H stretching vibration; this signal is expected to be identified in all MOs since all contain some type of peptide on their surface [41] , [42] , [43] . Signals c2 and h2 are associated with asymmetric stretches, whereas c3 and h3 are associated to symmetric stretches from C-H in CH 2 and CH 3 on the side chains of amino acids such as alanine, aspartic acid, or glycine [44] , [45] , [46] , fatty acids [47] and metabolites like to N-Acetyl-D-glucosamine (GlcNAc) which is a structural fragment constituting glycosylated proteins and chitin of C. albicans , but also, lipopolysaccharides in form of phosphorylated glucosamine of H. pylori [48] . In consequence, in term of nature of structural units, c2, c3, h2 and h3 do not provide important information for the differentiation of H. pylori and C. albicans biofilms formed from individually cultures nor from mixture of them, however, it is small shifts of signals could be used for the recognition of MOs on the surface.…”