Table 1.
Assignment of IR spectral features in skin. Results are reported from compilations in the literature [ref. 43–45], from other studies referenced here and from analysis of this study’s skin samples, including both clinical and engineered tissue a
Mode | Origin | Literature | Human skin |
Engineered skin |
||
---|---|---|---|---|---|---|
Epidermis | Dermis | Epidermis | Dermis | |||
Amide A (N–H stretching) | Peptide, protein | 3300 | 3298 | 3298 | 3292 | 3292 |
Amide B (N–H stretching) | Peptide, protein | 3080 | 3078 | 3078 | 3080 | 3082 |
C–H stretching of alkenes | Phospholipid, glycolipid, fatty acid, ceramide, triglyceride | 3010 | 3010 | 3010 | 3012 | 3012 |
Asymmetric CH3 stretching | Phospholipid, glycolipid, fatty acid, ceramide, triglyceride | 2957 | 2960 | 2960 | 2962 | 2958 |
Asymmetric CH2 stretching | Phospholipid, glycolipid, fatty acid, ceramide, triglyceride | 2920 | 2920 | 2920 | 2916 | 2918 |
Symmetric CH3 stretching | Phospholipid, glycolipid, fatty acid, ceramide, triglyceride | 2872 | 2868 | 2868 | 2874 | 2874 |
Symmetric CH2 stretching | Phospholipid, glycolipid, fatty acid, ceramide, triglyceride | 2851 | 2850 | 2850 | 2850 | 2850 |
CO stretch | Phospholipid | 1738 | 1740 | 1740 | 1738 | 1738 |
Amide I (80% CO stretch) | Peptide, protein, ceramide | 1655 | 1654 | 1654 | 1664 | 1664 |
Amide II (60% N–H in plane bend, 40% C–N stretch) | Peptide, protein, ceramide | 1545 | 1548 | 1548 | 1552 | 1550 |
CH2 scissoring | Phospholipid, glycolipid, fatty acid, triglyceride | 1468 | 1468 | 1468 | 1454 | 1460 |
CO stretch of COO– | Fatty acid | ~1395 | 1400 | 1400 | 1402 | 1392 |
CH3 symmetric bend | Phospholipid, fatty acid, triglyceride | 1378 | 1384 | 1384 | 1392 | 1390 |
CH2 wagging | Phospholipid, fatty acid, triglyceride | 1343–1370 | 1344 | 1338 | 1344 | 1336 |
Amide III (40% C–N stretch, 30% N–H in plane bend, 20% methyl–C stretch) | Collagen | 1283 | 1284 | 1284 | 1284 | 1284 |
Asymmetric PO2–stretch | Phosphate salt, nucleic acid, DNA, RNA | ~1245 | 1242 | 1240 | 1240 | 1238 |
Amide III (40% C–N stretch, 30% N–H in plane bend, 20% methyl–C stretch) | Collagen | 1236 | 1236 | 1234 | 1236 | 1236 |
Asymmetric PO2–stretch | Phosphate salt, nucleic acid, DNA, RNA | 1223 | 1224 | 1226 | 1224 | 1226 |
Amide III (40% C–N stretch, 30% N–H in plane bend, 20% methyl–C stretch) | Collagen | 1204 | 1204 | 1204 | 1204 | 1204 |
Ester C–O asymmetric stretch | Ester | 1170 | 1170 | 1168 | 1160 | 1170 |
Symmetric PO2–stretch | Phosphate salt, nucleic acid, DNA, RNA | ~1080 | 1082 | 1082 | 1082 | 1082 |
C–OP stretch | Phosphate ester | 1047 | 1056 | 1058 | 1034 | 1030 |