Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) Spectroscopy Analysis of Saliva for Breast Cancer Diagnosis

Table 3

Assignments of main wavenumbers indicated in the average original saliva ATR-FTIR spectra of Figure 1 and assignments based on different references [45–48].

Peak (cm^−1)	Proposed vibrational mode	Molecular source
1636	Amide I [ν (C=O), ν (C–N), δ (N–H)]	Protein
1549	Amide II [ν (N–H), ν (C–N)]	Protein
1447	CH3 asymmetric bending [δas (CH3)]	Protein (methyl groups)
1404	COO^− symmetric stretching [νs (COO^−)]	Lipid (fatty acids)/Protein (amino acids)
1350	Amide III [ν (C–N)]	Protein
1244
1045	C-O stretching, C-O bending of the C-OH groups [ν (C-O), δ (C-O)]	Carbohydrates (glycogen glucose, fructose)
995	C-O ribose/C-C; RNA uracil ring stretching	Nucleic acid (RNA)

ν = stretching vibrations, δ = bending vibrations, s = symmetric vibrations, as = asymmetric vibrations.