Vibrational Spectroscopy and Cancer - Vibrational Spectroscopy for Tissue Analysis - page 98

8. 1745 c m −1 can be found in normal tissues with fat cells. Thus, the
relative intensity of the band can reliably identify fat content of
tissue [94].
9. Protein bands:
• 1640 - 80 cm −1 : amide I
• 1220-300 cm −1 : amide III
• 928-40 cm −1 : ν(C-C) stretching (probably in amino acids proline
and valine) [71].
10. Protein band reflect the secondary protein structure [71].
11. The cellular cytoskeleton is composed of different kinds of pro-
tein fibres. Any depolymerization of these proteins would result
in unravelling of the secondary structure and hence an increase in
the NH 3 + and COO − vibrations (1485-1550 cm −1 and 1560-600 cm −1 ,
respectively) [128].
12. Cell cytoplasm, fat, collagen, and cholesterol have many of the same
functional groups (CH 2 bands, C-C stretches, etc.) [62].
13. 1121 cm −1 /1020 cm −1 ratio provides a measure of cellular RNA/DNA
ratio and is higher in malignant tissues than in normal ones [71,116].
14. 1045 cm −1 /1545 cm −1 ratio gives an estimate of carbohydrate concen-
tration in cells and is lower in malignant tissues than in normal
ones [116].
15. Amide II region is not as sensitive to conformational changes as
amide I [104].
16. The peak area of 1030 cm −1 /1080 cm −1 corresponds to the glycogen/
phosphate ratio and is indicative of metabolic activity. This ratio has
been used to differentiate neoplastic from non-neoplastic cells of dif-
ferent cancers [86].
1 7. The spectra of amide I vibrational modes of the proteins are highly
sensitive to conformational changes in the secondary structure [60].
18. The frequencies and relative intensities of the characteristic protein
vibrations (amide I, II, III) depend on the secondary structure that the
protein assumes (e.g., helical, sheet, globular, or triple-helical) [32].
19. Both amide I and III have some overlapping with nucleic acid fre-
quencies. Therefore, these spectral regions cannot be used to quan-
tify the components in mixtures of protein and nucleic acids. The
spectral features between 1000 cm −1 and 1150 cm −1 are reasonably
specific for nucleic acids in the absence of glycogen [32].
20. It is thought that unsaturated lipids existing in nature predomi-
nantly take the cis configuration of the C=C double bond [180,181].
The cis configuration is known to increase the flexibility of lipid
membranes, while the trans makes them stiff.