Table 1.

Main infrared absorbance band integrals of proteins, lipids and carbohydrates

#	Primary contributing biomolecules	Wavenumber (cm−1)	Band assignments
1	Unsaturated lipids	~3010	ν(=C–H)
2	Saturated lipids	~2965	νas(C–H) of methyl group (CH3)
		~2925	νas(C–H) of methylene group (CH2)
		~2875	νs(C–H) of methyl group (CH3)
		~2845	νs(C–H) of methylene group (CH2)
3	Lipid esters	~1735	ν (C=O) of esters
4	Amino acid side chains, nucleic acids	~1715–1690	ν (C=O) of carbonic acids
5	Proteins	~1695–1610	amide I (predominantly ν (C=O) coupled with ν (C–N), δ(N–H))
		~1550	amide II (ν (C–N) coupled with δ(N–H))
		~1310–1240	amide III
6	Nucleic acids, phosphorylated proteins, phospholipids	~1250–1220	νas(P=O) of phosphodiesters (PO2−)
7	Collagen	~1210–1200	ν (C–O) band centered at ~1204 cm−1
8	Carbohydrates, nucleic acids, phospholipids and proteins	~1130–900	ν (C–O–C), ν (C–O), ν (C–C), ν (C–O–P), ν (P–O–P)
9	Nucleic acids, phosphorylated proteins, phospholipids	~1080	νs(P=O) of phosphodiesters (PO2−)

Notes: Adapted from [19]. ν– stretching, s – symmetric, as – asymmetric.