## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c} \hline \hline
**Spectral Position (cm\({}^{-1}\))** & **Assignment** \\ \hline
1087 & symmetric PO\({}_{2}\)\({}^{-}\) stretching of nucleic acids \\ \hline
1167 & C-OH stretching of proteins \\ \hline
1236 & asymmetric PO\({}_{2}\)\({}^{-}\) stretching of nucleic acids \\ \hline
1310 & amide III of proteins \\ \hline
1395 & COO\({}^{-}\) stretching of proteins and lipids \\ \hline
1455 & CH\({}_{3}\) bending of proteins and lipids \\ \hline
1542 & amide II of proteins \\ \hline
1645 & amide I of proteins \\ \hline
1740 & C=O stretching of lipids \\ \hline
2852 & symmetric CH\({}_{2}\) stretching of lipids \\ \hline
2875 & symmetric CH\({}_{3}\) stretching of proteins and lipids \\ \hline
2921 & asymmetric CH\({}_{2}\) stretching of lipids \\ \hline
2958 & asymmetric CH\({}_{3}\) stretching of proteins and lipids \\ \hline
3012 & CH stretching of lipids \\ \hline
3066 & N-H stretching of amide B \\ \hline
3290 & N-H stretching of amide A \\ \hline \end{tabular}
\end{table} 
Table 1: Assignment of FTIR spectral structures, according to previous results reported in the literature [42] and in the present investigation. Figure 2: Mean FTIR spectrum of healthy FHC cells (black lines) after the SNV normalisation. The spectral position of the absorption features, as deduced by minima of the second derivative spectra (red continuous lines), is indicated by dash-dotted lines. The wavenumber position is reported for each spectral feature. The spectra have been vertically shifted for clarity purposes. [PERSON] et al., regarding colon tissue [43]. In addition, [PERSON] et al. found a greater intensity of lipid FTIR peaks in healthy colon tissue with respect to cancerous tissue and post-chemotherapy tissue. They proposed that the intensity values of these spectral peaks (as well as those from nucleic acids and protein components) be considered as markers in diagnostic management and treatment monitoring for colorectal cancer [9]. However, although a significant statistical difference between the distributions of absorption values in the two groups of cells can be deduced from Figure 3a,b (as indicated by the box plots on the right side), the separation was not sharp, and several absorption intensities were similar between the two cell types. Also, the intensity values of some protein-related FTIR peaks were quite different for the two types of cells: they are shown in Figure 3c,d for the amide II and amide I peaks, respectively. In particular, the absorption values of cancerous cells were larger than those of healthy ones and the differences were statistically significant. Such a result is in good  
Figure 3: Distribution of intensity values of some spectral features due to the lipid ((**a**) 1740 cm\({}^{-1}\) and (**b**) 2921 cm\({}^{-1}\)), protein ((**c**) 1542 cm\({}^{-1}\) and (**d**) 1645 cm\({}^{-1}\)), and DNA ((**e**) 1087 cm\({}^{-1}\) and (**f**) 1236 cm\({}^{-1}\)) components of healthy (black dots) and cancerous (blue dots) colon cells. The corresponding box plots of each distribution are shown on the right-hand side. agreement with that reported by [PERSON] et al. regarding FTIR microspectroscopy of collagen from human colon specimens which was surgically removed after diagnosis of adenocarcinoma [44]: they found larger FTIR spectral signals from malignant tissue than normal tissue in the amide III spectral range [44]. Even [PERSON] reported that protein-related peaks in the Raman spectra of Caco-2 cells were characterized by greater intensities with respect to the corresponding peaks in the Raman spectra of noncancerous colon cells [45]. However, discordant results have also been reported [9], and, in addition, in Figure 3c,d, many similar and not clearly distinct intensity values for the two cell types are evident, particularly as far as the amide I peak is concerned.