Spectroscopy and Molecular Changes in Cancer Cells - Vibrational Spectroscopy for Tissue Analysis - page 26

stretching. Some other research groups have used almost exactly the same
peaks for analysing cervical malignancies [28,29] and prostate cancers [30]. It
was concluded that the vibrations of the PO 2 − were mainly due to phosphodi-
ester groups on nucleic acids, and phosphate groups of phospholipids do not
generally contribute to these bands. In addition, it was noted that the spectra
of DNA and RNA display extremely weak peaks at 1399 cm −1 and 1457 cm −1 .
Proteins and carbohydrates showed bands at 1173 cm −1 , due to CO stretch-
ing of C-OH groups of serine, threonine, and tyrosine. Proteins also had
characteristic bands at 1396 cm −1 and 1449 cm −1 . These bands were related to
symmetric and asymmetric CH 3 bending. Lipid bands were distinguished at
1469 c m −1 due to CH 2 bending of acyl chains. One of the interesting findings
of this group was the interpretation of the 1153, 1161, and 1172 cm −1 spectral
bands. The peaks at 1153 and 1161 cm −1 were assigned to stretching vibra-
tions of hydrogen bonding C-OH groups, whereas the band at 1172 cm −1
was due to the stretching vibrations of nonhydrogen bonded C-OH groups.
Using these peaks it was concluded that the loss of hydrogen bonding of the
C-OH of amino acid residues of proteins in lung cancer could be observed
spectroscopically. In addition, it was found that the malignant cells display
decreased intensity of the PO 2 − (asym) band, and increased intensity of the
PO 2 − (sym) band.
Yano et al. [31] focused on peak intensities of 1545 cm −1 (protein), 1467 cm −1
(cholesterol, methylene band), 1084 cm −1 (DNA, PO 2 − vibrations), and 1045 cm −1
(glycogen, OH stretching coupled with bending) in cancerous lung tissue.
It was recognised that in cancerous tissues, levels of DNA and glycogen
increase and cholesterol decreases. They found that the H1045:H1467 ratio
is an exceptionally useful factor for discrimination of cancerous tissues
from noncancerous ones. In other words, if this ratio is larger than 1.4, one
can say with confidence that tissue contains squamous cell carcinoma or
adenocarcinoma.
Eckel et al. [32] focused on five different regions for peak intensity analysis
of human breast samples. These areas are as follows:
1. The amide A and B bands stemming from N-H stretching modes in
proteins and nucleic acids (3300 and 3075 cm −1 , respectively).
2. The amide I band region (1600-1720 cm −1 ) of proteins. It was con-
cluded that 1657 cm −1 can be assigned to the α-helical structure and
1635 cm −1 to the β-sheet structure, while peaks at 1649 cm −1 and
1680 cm −1 are mainly due to unordered random coils and turns.
3. The amide II band region (1480-1600 cm −1 ) of proteins.
4. The amide III band region (1180-1300 cm −1 ) of proteins. Gniadecka
et al. did a similar study on human basal cell carcinoma samples [33].
However, the region considered to be due to the amide I and III bands
are a bit different in this study. They mentioned 1640-1680 cm −1 as
amide I and 1220-1330 cm −1 as the amide III region. In addition,