Vibrational spectra calculation of squamous cell carcinoma in the amide band region

• Published in: Vibrational spectroscopy Vol. 97; pp. 135 - 139
• Main Authors: Bortoletto, Daiana R., Lima, Cassio A., Zezell, Denise, Sato, Erika T., Martinho, H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-07-2018; Elsevier BV
• Subjects: Amino acids; Cancer; Computational simulation; Density Functional Theory; First principles; Fourier transforms; FTIR; Infrared spectroscopy; Mathematical models; Optical biopsy; Proline; Proteins; Sheet modelling; Skin; Skin cancer; Spectrum analysis; Squamous cell carcinoma; Tissue computer model; Tissues; Tumors; Vibration; Vibrational spectra; Vibrational spectroscopy; Squamous cell carcinoma; Optical biopsy; FTIR; Density Functional Theory; Computational simulation; Tissue computer model; Vibrational spectroscopy; Skin cancer
• ISSN: 0924-2031; 1873-3697
• DOI: 10.1016/j.vibspec.2018.06.007

Alterations in the amide (1500–1700 cm−1) spectral region probed by Fourier-transform infrared spectroscopy (FTIR) have been reported comparing tumor and normal tissues. Usually, bands in this range are assigned to the so-called Amide I, II, and III vibrations which provide pieces of information concerning peptide bonds and secondary structure (α-helix, β-sheet) of proteins. Proteins folding changes due to tumoral process are usually considered to qualitatively explain the observed differences between tumor and normal tissues. In this paper, the observed changes in the FTIR spectra of squamous cell carcinoma compared to normal tissues were analyzed by First-Principles Density Functional Theory vibrational calculations. Computational models for skin and prototype β-sheet model were employed. Our findings shown that predominates conjugated Amide I + Amide II, Amide V, methylene torsions, and ring side chains torsions and swings vibrations in this region. We also notice the lack of evidence concerning changes in the secondary structure of the β-sheet peptidic model to explain the spectral differences. In fact, we concluded that the proline amino acid has the main rule to explain the data in this region being it responsible for the strong coupling between vibrations instead of water.