Table 1.
Raman peaks detected in the average spectra from the decellularized matrices (unlabeled samples) acquired in the spectral region from 0 to 3800 cm−1. Known peaks from vibrational assignments are included (some with small shifts).
| Peaks (cm−1) | Assignments | References |
|---|---|---|
| 322 | CaF2 | [44,45] |
| 404 | Found in D(+)−glucose and glycogen | [46] |
| 420 | C-C=O in-plane deformation. Cholesterol. Found in D(+)−glucose and D(+)−galactose | [46,47,48] |
| 429 | Cholesterol. Cholesterol ester | [48,49] |
| 432 | Found in glycogen | [46] |
| 457 | Ring torsion of phenyl | [48] |
| 490 | Glycogen. Found in D(+)−galactose | [46,48,49] |
| 516 | S-S vibration of type IV collagen | [50] |
| 519 | Phosphatidylinositol. Found in aggrecan | [48,49,51] |
| 546 | Cholesterol content. Found in chondroitin sulfate. S-S vibration of type IV collagen | [48,49,50] |
| 556 | Beta(OCO), Beta(CCC), Beta(CCO). Found in D(+)−glucose | [46] |
| 570 | C-C=O in-plane deformation. Cholesterol. Tryptophan/cytosine. Guanine | [47,48] |
| 593 | Beta(CCC), ring deformation. Found in glycogen | [46] |
| 608 | Cholesterol. Ring deformation of phenyl | [48,49,52] |
| 622 | Protein peak. Phenylalanine | [25,48] |
| 625 | (600–900 cm−1) CH out-of-plane bending vibrations | [48] |
| 643 | C-C twisting mode of tyrosine. Found in aggrecan monomers and aggregates | [25,48,49,51,52] |
| 654 | 630–70 cm−1 ν(C–S) gauche (amino acid methionine). Found in D(+)−glucose | [46,48] |
| 667 | C-S stretching mod of cysteine (collagen type I). Found in D(+)−galactose | [46,48,49] |
| 700 | ν(C-S) trans (amino acid methionine). C-N stretching mode from the choline head in phosphatidylcholine and sphingomyelin. Found in D(+)−galactose | [25,46,48,49,52] |
| 720 | C-N (membrane phospholipid head/ nucleotide peak. Symmetric stretch of choline group N+(CH3)3. Characteristic of phospholipids. Phosphatidylcholine. Sphingomyelin. DNA. δ(=C-H) in-plane in triglyceride-rich lipoproteins | [48,49,52,53] |
| 804 | Left-handed helix DNA (Z form) | [48] |
| 817 | C-C stretching (collagen assignment). More intense in collagen type I | [48,49,50,52] |
| 829 | C2’ conformation of sugar. Tyrosine | [25,48] |
| 830 | Proline. Hydroxyproline. Tyrosine. n2 PO2 (−) stretch of nucleic acids. Found in D(+)−galactose | [25,46,48,49,52] |
| 838 | Deformative vibrations of amine groups. Found in D(+)−glucose | [46,48,49,52] |
| 850 | Most probably due to single bond stretching vibrations for the amino acids and valine and polysaccharides. Tyrosine (Fermi resonance of ring fundamental and overtone). Single bond stretching vibrations for the amino acids and valine and polysaccharides. Tyrosine. C-C stretching. Found in aggrecan and chondroitin sulfate. More intense in collagen type IV | [25,48,49,50,51,52] |
| 875 | Antisymmetric stretch vibration of choline group N+ (CH3)3. Characteristic for phospholipids. Phosphatidylcholine. Sphingomyelin. ν(C-C) hydroxyproline (protein assignment). C-C stretching hydroxyproline (collagen assignment). More intense in collagen type IV | [25,48,49,50,52] |
| 891 | Saccharide band (overlaps with acyl band). Found in D(+)−galactose. Found in hyaluronic acid and chondroitin sulfate | [46,48,49,51,52] |
| 928–40 | ν(C-C) stretching probably in amino acids proline and valine (protein band). More intense in collagen type IV | [48,49,50] |
| 938 | Proline. Hydroxyproline. n(C-C) skeletal of collagen backbone. C-C stretch backbone. Found in glycogen. | [46,48,49,52] |
| 950–3 | Most probably due to single-bond stretching vibrations for the amino acids proline and valine and polysaccharides. CH6′.5′ out of plane | [48] |
| 961 | Tryptophan ring breathing; C–O deoxyribose. C–C. Found in D(+)−galactose. Appears in brain tissue | [46,49,54] |
| 972 | C-C backbone (collagen assignment). OCH3 (polysaccharides. pectin). Found in D(+)-galactose. DNA. δ(=C-H) out of plane in triglyceride-rich lipoproteins | [46,48,49,52,53] |
| 989 | Ring stretch modes of benzene derivatives. Appears in brain tissue. Phenylalanine NADH | [48,54] |
| 996 | C-O ribose. C-C. Carbohydrates peak for solutions and solids. Carbohydrates (weak shoulder). Found in D(+)−galactose | [46,48,49] |
| 1004 | Phenylalanine (of collagen; protein assignment). νs(C-C). Symmetric ring breathing. Phenyl breathing mode. ν(C-C) phenylalanine. Found in D(+)−glucose. More intense in collagen type IV. Decreased at the injured brain | [46,48,49,50,52,55] |
| 1012 | CHα.α’ out-of-plane bending and Cα= Cα’ torsion | [48] |
| 1064 | Skeletal C-C stretch of lipids. Acyl chains. ν(C-C) trans. stretching C-O ribose. CO stretching and C-O-C stretching and PO2 symmetric stretch. Found in D(+)−galactose. Found in chondroitin sulfate, and aggrecan monomers and aggregates. ν(C-C) in triglyceride-rich lipoprotein particles | [25,46,48,49,51,52,53] |
| 1074 | Glucose. Triglycerides. C-C (lipid). Found in D(+)-glucose. ν(C-C) in triglyceride-rich lipoprotein particles | [46,49,53] |
| 1085 | ν(C-C) gauche. PO2 asymmetric stretching of phospholipids and nucleic acid | [25,52] |
| 1086 | ν(C-C) gauche. Symmetric phosphate stretching modes or ν(PO2−)sym (phosphate stretching modes originate from the phosphodiester groups in nucleic acids and suggest an increase in the nucleic acids in the malignant tissues). PO2− symmetric. ν(PO2−) symmetric stretching of phosphodiesters. Found in glycogen | [46,48,49,52] |
| 1095 | Lipid. ν(C-N). Phosphodioxy group (PO2- in nucleic acids). Stretching PO2(−) symmetric. DNA: O–P–O backbone stretching | [48,52] |
| 1130 | C-C skeletal stretch trans conformation in lipids. Phospholipid structural changes (trans versus gauche isomerism). Acyl chains. CH3 deformations (both symmetric and asymmetric). Found in glycogen | [46,48,49,52] |
| 1268 | (=C-H) (phospholipids). Ring stretch. Amide III (collagen assignment). Found in glycogen. δ(=C-H) in plane cis | [46,48,49,52,53] |
| 1274 | Amide III. Found in D(+)−glucose. More intense in collagen type IV | [46,48,50] |
| 1298 | Palmitic acid. Acyl chains. Fatty acids. Phospholipid CH2 twist and wagging. amide III (a fibrous). CH3/CH2 twisting or bending of lipid/collagen | [25,48,49,54] |
| 1438 | Lipid. δ(CH2) δas(CH3) in lipid. CH2 deformation. δ(CH2) scissor in triglyceride-rich lipoprotein particles. Fatty acids, CH2 (lipids and proteins) | [25,48,49,53,54] |
| 1452 | CH2 bending mode of proteins. CH2CH3 deformation. CH2 deformation in lipids. δ(CH2) in triglyceride-rich lipoprotein particles | [48,49,53] |
| 1458 | CH3 deformation. CH2 deformation. Nucleic acid modes. DeltaCH3 of collagen. Amide (III) stretch. Found in D(+)−glucose and glycogen | [46,48,49,52,56] |
| 1549 | Amide II of proteins. | [48,54] |
| 1657 | Fatty acids. Amide I (collagen assignment). Triglycerides (fatty acids). α-helical structure of amide I. ν(C=C) cis (lipid), and ν(O-H) (water) in triglyceride-rich lipoprotein particles. Decreased in the injury brain | [25,48,49,52,53,55] |
| 1670 | Amide I. C=C stretching vibrations. Cholesterol & its esters C=C stretching vibration mode of steroid ring; Amide I (anti-parallel β-sheet). ν(C=C) trans. Lipids. Fatty acids. | [27,48,49,52] |
| 2330 | Atmospheric N2 | [49,54] |
| 2341 | Asymmetric stretching band of CO2− hydrates | [48] |
| 2677 | Stretching N-H(NH3+) | [48] |
| 2704 | 2700–3000 C-H stretches. Stretching vibrations of CH. NH. and OH groups | [48] |
| 2711 | 2700–3000 C-H stretches. Stretching vibrations of CH. NH. and OH groups | [48] |
| 2719 | 2700–3000 C-H stretches. Stretching vibrations of CH. NH. and OH groups | [48] |
| 2727 | Stretching N-H (NH3+) | [48] |
| 2734 | 2700–3000 C-H stretches. Stretching vibrations of CH. NH. and OH groups | [48] |
| 2768 | Stretching N-H(NH3+) | [48] |
| 2775 | 2700–3000 C-H stretches. Stretching vibrations of CH. NH. and OH groups | [48] |
| 2848 | Cholesterol. Phospholipids and creatine (higher in normal tissues). Stretching vibrations of CH2 and CH3 of phospholipids. Cholesterol and creatine. Found in D(+)−galactose. CH2 symmetric stretching vibrations | [25,46,48,57] |
| 2861 | Stretching C-H | [48] |
| 2865 | C=O | [48] |
| 2868 | Symmetric stretching of methoxy (3) | [48] |
| 2874 | νCH3. stretching C-H. N-H. CH3 symmetric stretch of lipids; CH2 symmetric stretch of lipids | [48,49,54] |
| 2882 | Stretching C-H. Asymmetric vibration of CH2. Found in D(+)−glucose | [25,46,48] |
| 2891 | Stretching C-H. Found in D(+)−glucose | [46,48] |
| 2898 | CH3 symmetric stretch | [48] |
| 2904 | CH3 stretching modes (both symmetric and asymmetric) | [48] |
| 2910 | CH3 stretching vibrations. Found in glycogen | [46,48,49] |
| 2915 | CH band of lipids and proteins. Found in D(+)−galactose. Appears in brain tissue | [46,48,49,54] |
| 2939 | Asymmetric stretching of methoxy(2). Symmetric vibration of CH3. Found in D(+)−glucose. CH3 symmetric stretching vibrations | [25,46,48,57] |
| 2952 | CH3 stretching vibrations. CH3 asymmetric stretch | [48] |
| 2959 | C-H stretching. νCH3 of lipids. DNA and proteins. Asymmetric stretching mode of the methyl groups from cellular proteins. Nucleic acids and lipids. Asymmetric stretching of methoxy (2) | [25,48] |
| 2960 | νasCH3; Out-of-plane chain-end antisymmetric CH3 stretch band | [48,49] |
| 2964 | CH3 modes. Found in D(+)−glucose | [46,48] |
| 2971 | Asymmetric stretching of methoxy(4) | [48,49,52] |
| 2975 | Stretching N-H. Stretching C-H. Found in D(+)−galactose | [46,48,49] |
| 2982 | C-H | [48] |
| 2990 | C-H ring/ C-H | [48] |
| 3005 | 3000–600 cm−1 C-H stretching | [48] |
| 3012 | Unsaturated = CH stretch | [48] |
| 3018 | CH2′ aromatic stretch | [48] |