Research Article
Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) Spectroscopy Analysis of Saliva for Breast Cancer Diagnosis
Table 4
Assignments of FTIR peaks of the average second-derivative spectra and assignments based on different references [
45–
51].
| | 2nd derivative peak (cm−1) | Proposed vibrational mode | Molecular source |
| | 2964 | CH3 asymmetric stretching (νas (CH3)) | Lipid | | 2929 | CH2 asymmetric stretching (νas (CH2)) | Nucleic acid/Lipid | | 2875 | CH3 symmetric stretching (νs (CH3)) | Lipid | | 2659 | Unassigned band | | | 2358 | O=C=O stretching | Carbon dioxide | | 2322 | Unassigned band | | | 2285 | N=C=O stretching | Nitrile | | 2059 | C-N stretching of thiocyanate anions (SCN−) | Thiocyanate | | 1635 | Amide I (β-sheet structure) | Protein | | 1544 | Amide II | Protein | | 1450 | CH2 symmetric bending (δs (CH2))
Methylene bending | Lipid and protein | | 1404 | CH3 symmetric bending (δs (CH3)) | Protein (methyl groups) | | 1313 | Amide III | Protein | | 1242 | Amide III
PO2− asymmetric stretching (νas (PO2−)) | Protein
Nucleic acid | | 1159 | C-O stretching (ν (C-O))
CO–O–C asymmetric stretching (νas (CO-O-C)) | Protein/CarbohydrateLipid | | 1120 | Phosphorylated saccharide residue
Mannose-6-phosphate | Carbohydrate
Protein (glycoprotein) | | 1041 | PO2− symmetric stretching (νs (PO2−)) | Nucleic acid (RNA/DNA) and glycogen | | 987 | C=C bending | Monosaccharides and polysaccharides | | 877 | C3’endo/anti A-form helix | Nucleic acid | | 613 | C-H out-of-plane bending | Cell membranes |
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ν = stretching vibrations, δ = bending vibrations, s = symmetric vibrations, as = asymmetric vibrations.
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