Vibrational Spectroscopy and Cancer - Vibrational Spectroscopy for Tissue Analysis - page 97

number of studies involving spectroscopy of cancer tissues and the use is
growing rapidly. There is a growing need to identify the key spectral peaks
and their correct assignment to the chemical structures. Therefore, it is of
utmost importance to have a trustworthy spectral database that is widely
available to researchers working with vibrational spectroscopic techniques.
The following are some spectral peaks that are considered extremely impor-
tant in correctly assigning spectral peaks related to biological molecules:

1. Lipid bands mainly consist of three kinds of bands: C-H, C=C, and
C- O [61].

2. Collagen, the major protein of connective tissue, contains approxi-
mately 33% glycine, and 20-25% praline, and hydroxyproline resi-
dues [63].

3. The vibrational modes of collagen are as follows:

A. 1634 and 1654 cm −1 : amide I

B. 1544 cm −1 : amide II

C. 1450 and 1401 cm −1 : bending modes of methyl groups

D. 1337, 1280, 1237, 1204 cm −1 : amide III and CH 2 wagging vibrations

from glycine backbone and praline side chains

E. 1082 and 1031 cm −1 : carbohydrate residues of collagen [63].

4. The vibrational modes of collagen type I are as follows:

A. 1163 and 1174 cm −1 : tyrosine

B. 937 cm −1 : proline

C. 856 cm −1 : hydroxyproline

D. 667 cm −1 : cysteine [93]

5. The protein amide I characteristics (peak frequency and width) are
determined by conformational differences like α-helix, β-plates, and
disordered structure [85].

6. The vibrational modes of lipids are as follows:

A. 1750 cm −1 : C=O

B. 1655 cm −1 : C=C

C. 1437 cm −1 : CH 2 (1420 -1450 c m −1 ) [71]

D. 1301 cm −1 : assigned for Parker (1300 cm −1 ) [71]

E. 1267 cm −1 : CH

F. 1076 cm −1 : C-C [93]

7. Two possible assignments are available for the carbonyl band at
about 1745 cm −1 :
• Phospholipid band in the membrane
• Ester group in fat (the carbonyl band of phospholipids) [94]