## 3 Results and Discussion
### Analysis of Relative Absorbance Ratios (t\({}_{0}\) and t\({}_{24}\) Cells)  
The intensity of an infrared band is proportional to the concentration of the species that are associated with the band. However, the use of band absorbance values themselves for quantitative analysis can cause experimental artifacts such as variations in sample thickness. For this reason, it is preferable to use their ratios [18; 19; 20]. In Table 1, the ratios between the absorbance of selected bands used in this work are reported, with an indication of the biological processes to which they are related. In Figure 5A-C the ratio values PR1, PR2, and PR3 are reported, for the different doses and times of fixation; all these ratios are mainly related to protein rearrangement (see Table 1). In detail, PR1 is evaluated as the ratio between the absorbance value of the Amide I bands and the \(\alpha-\)helix subcomponent of Amide II bands; PR2 is estimated as the ratio between the absorbance value of the Amide I band and the absorbance of the \(\beta-\)sheet subcomponent of Amide II band, and PR3 is given by the ratio of between the absorbance value of the \(\alpha-\)helix subcomponent and the absorbance of the \(\beta-\)sheet subcomponent of Amide II band. The ratio between the absorbance of Amide I and Amide II bands (PR1) shows a significant decrease (\(p\leq 0.05\)) at all doses for t\({}_{0}\) cells, while for the t\({}_{24}\) cells, values higher than for the 0 Gy sample are shown for all doses, except the 10 Gy one. PR2 shows a decrease for the t\({}_{0}\) cells, compared to the control, at 6 Gy (\(p\leq 0.05\)) and a significant increase at 8 and 10 Gy (\(p\leq 0.05\)), while the PR3 ratio shows increasing values for all doses (\(p\leq 0.05\)). Conversely, for t\({}_{24}\) cells, values lower than those of the unirradiated sample are visible for all doses for both ratios. The changes occurring in PR1, PR2, and PR3 values are due to changes in the secondary structure of proteins and can be also correlated with the above-mentioned changes in the contribution of enzymes (that are mainly proteins) involved in DNA repair processes. Further information about the changes in the secondary structure of the protein component of cells will be reported in the following Section 3.5. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & & & & \\ \hline
**0 Gy** & & **2 Gy** & **4 Gy** & **6 Gy** & **8 Gy** & **10 Gy** \\ \hline
**Peak** & & **Peak** & **Peak** & **Peak** & **Peak** & **Peak** \\
**(cm\({}^{-1}\))** & & **(cm\({}^{-1}\))** & **(cm\({}^{-1}\))** & **(cm\({}^{-1}\))** & **(cm\({}^{-1}\))** & **(cm\({}^{-1}\))** \\ \hline
2955 & p, 1 & 2959 (+4) & 2958 (+3) & 2959 (+4) & 2958 (+3) & 2958 (+3) \\
2921 & 1 & 2921 & 2921 & 2922 (+1) & 2922 (+1) & 2922 (+1) \\
2886 & p, 1 & 2883 (\(-\)3) & 2883 (\(-\)3) & 2890 (+4) & 2890 (+4) & 2890 (+4) \\
2852 & 1 & 2851 (\(-\)1) & 2851 (\(-\)1) & 2851 (\(-\)1) & 2852 & 2852 \\
1646 & P & 1648 (+2) & 1649 (+3) & 1647 (+1) & 1648 (+2) & 1645 (\(-\)1) \\
1547 & P & 1549 (+2) & 1553 (**+6**) & 1546 (\(-\)1) & 1550 (+3) & 1546 (\(-\)1) \\
1522 & P & 1528 (**+6**) & 1529 (**+7**) & 1529 (**+7**) & 1527 (**+5**) & 1520 (\(-\)2) \\
1452 & p, 1 & 1450 (\(-\)2) & 1448 (\(-\)4) & 1448 (\(-\)4) & 1447 (\(-\)5) & 1448 (\(-\)4) \\
1398 & P & 1398 & 1399 (+1) & 1400 (+2) & 1400 (+2) & 1398 \\
1235 & DNA, c & 1233 (\(-\)2) & 1225 (**-10**) & 1232 (\(-\)3) & 1230 (**-5**) & 1229 (**-6**) \\
1078 & DNA & 1071 (**-7**) & 1090 (**+12**) & 1085 (**+7**) & 1090 (**+12**) & 1087 (**+9**) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average FTIR peak positions for control and samples treated with different doses of X-rays fixed 24 h after irradiation. The shifts in terms of units of wavenumber are indicated in brackets for the 0 Gy spectrum stands for shifts with respect to the values found for the control spectrum (t0); bold values stand for shifts greater than the spectral resolution of the instrument 4 cm\({}^{-1}\). Abbreviations: p = proteins, l = lipids, c = carbohydrates.