Assignments of some important absorption regions and characteristic group frequencies in the IR spectra of brain tissue
| Spectral region/frequency | Assignment |
|---|---|
| 3050-2800 cm−1 | Dominated by C—H stretching vibrations of fatty acids (mostly of membrane lipids) |
| 3012 cm−1 | C—H stretching of alkenes |
| 2959 cm−1 | Antisymmetric stretching of >CH3 groups |
| 2921 cm−1 | Antisymmetric stretching of >CH2groups |
| 2872 cm−1 | Symmetric stretching of >CH3 groups |
| 2851 cm−1 | Symmetric stretching of >CH2 groups |
| 1800-1500 cm−1 | Dominated by absorption of proteins |
| 1738 cm−1 | >CO stretching vibration of ester carbonyl of phospholipids |
| 1656 cm−1 | Amide I band of proteins |
| 1544 cm−1 | Amide II band of proteins |
| 1466 cm−1 | C—H bending vibration of >CH2groups of lipids, proteins, and nucleic acids |
| 1390 cm−1 | >CO stretching vibration of COO−groups |
| 1300-1000 cm−1 | “Fingerprint region,” originating from characteristic C—O—P, C—O—C, and C—C vibrations of DNA/RNA, carbohydrates, lipids, and proteins and PO stretching vibrations of nucleic acids and phospholipids |
| 1240 cm−1 | Antisymmetric PO stretching vibration |
| 1080 cm−1 | Symmetric PO stretching vibration |