## 3 Results and Discussion
### Analysis of Infrared Spectra from Cells Fixed 24 h after Irradiation (t\({}_{24}\) Cells)  
The average spectra for samples that were exposed to increasing doses of X-rays, fixed 24 h after irradiation (t\({}_{24}\) cells), are reported in Figure 4A for the HWR region and in Figure 4B for the fingerprint region, respectively. As in the previous case, they present some wavenumber shifts and some differences in peak absorbance. In Table 3, the position of peaks for samples exposed to different doses are reported. The shifts, in terms of wavenumber, of peak positions with respect to that found for the unirradiated t\({}_{24}\) samples are also reported; shifts higher than the spectral resolution available in our experiments are reported in bold characters. Figure 3: Comparison of average Fourier transform infrared (FTIR) spectra in the region 3000–2700 cm\({}^{-1}\) (**A**) and in the region 1800–900 cm\({}^{-1}\) (**B**) between the control cells (0 Gy) and irradiated cells (2, 4, 6, 8, 10 Gy) fixed immediately after irradiation; the spectra are shifted in absorbance to allow the comparison, data are presented as MEAN \(\pm\) SD. Differently from the t\({}_{0}\) cells, in the HWR region, there are no significant shifts, while in the fingerprint region, shifts are visible for different peaks. The Amide II band peak (1547 cm\({}^{-1}\)) shows variations only at 4 Gy, while the peak at 1522 cm\({}^{-1}\) changes at all the doses except for 10 Gy; the band at 1452 cm\({}^{-1}\), linked to protein and lipid molecule vibrations, shows a shift at 8 Gy dose. The band at 1235, linked mainly to PO\({}_{2}\)\({}^{-}\) DNA stretching, still shows shifts at 4, 8, and 10 Gy; conversely, the band at 1078 cm\({}^{-1}\), similarly linked to PO\({}_{2}\)\({}^{-}\) DNA stretching, shows shifts for all the doses. As said before, these shifts can be due to changes in the DNA conformation. The difference of the shifts with respect to the t\({}_{0}\) cells, in which significant shifts are observed only for high doses (8-10 Gy), may offer an \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & & & & \\ \hline
**0 Gy** & \multicolumn{2}{c}{**2 Gy**} & \multicolumn{2}{c}{**4 Gy**} & \multicolumn{2}{c}{**6 Gy**} & \multicolumn{2}{c}{**8 Gy**} & \multicolumn{2}{c}{**10 Gy**} \\ \hline
**Peak** & \multicolumn{2}{c}{**Peak**} & \multicolumn{2}{c}{**Peak**} & \multicolumn{2}{c}{**Peak**} & \multicolumn{2}{c}{**Peak**} & \multicolumn{2}{c}{**Peak**} \\
**(cm\({}^{-1}\))** & \multicolumn{2}{c}{**(cm\({}^{-1}\))**} & \multicolumn{2}{c}{**(cm\({}^{-1}\))**} & \multicolumn{2}{c}{**(cm\({}^{-1}\))**} & \multicolumn{2}{c}{**(cm\({}^{-1}\))**} \\ \hline
2955 & p,1 & 2956 (+1) & 2957 (+2) & 2957 (+2) & 2958 (+3) & 2959 (+4) \\
2922 & l & 2922 & 2922 & 2922 & 2922 & 2923 (+1) \\
2870 & p,1 & 2877 (+7) & 2874 (+4) & 2885 (**+15**) & 2888 (**+18**) & 2888 (**+18**) \\
2851 & l & 2851 & 2851 & 2851 & 2852 (+1) & 2852 (+1) \\
1652 & p & 1651 (-1) & 1651 (-1) & 1649 (-3) & 1648 (-4) & 1649 (-3) \\
1553 & p & 1550 (-3) & 1551 (-2) & 1550 (-3) & 1547 (-6) & 1544 (-9) \\
1527 & p & 1523 (-4) & 1525 (-2) & 1528 (+1) & 1522 (-5) & 1515 (-12) \\
1455 & p,1 & 1455 & 1455 & 1452 (-3) & 1451 (-4) & 1452 (-3) \\
1396 & P & 1398 (+2) & 1397 (+1) & 1399 (+3) & 1402 (**+6**) & 1407 (**+11**) \\
1246 & DNA, c & 1248 (+2) & 1247 (+1) & 1243 (-3) & 1240 (-6) & 1241 (-5) \\
1082 & DNA & 1081 (-1) & 1082 & 1084 (+2) & 1083 (+1) & 1088 (**+6**) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average FTIR peaks position for control and samples treated with different dose of X-rays fixed immediately after irradiation. The shifts in terms of units of wavenumber are indicated in brackets (bold values stand for shifts greater than the spectral resolution of the instrument 4 cm\({}^{-1}\)). Abbreviations: p = proteins, l = lipids, c = carbohydrates.