## 3 Results
### Structure Analysis  
To better understand the radiation damage, we determined the crystal structures of Thaumatin18 and Thaumatin100 ms at 1.13 A resolution. The R\({}_{\text{work}}\)/R\({}_{\text{free}}\) of Thaumatin18 and Thaumatin100 ms were 18.36/19.24 and 17.06/17.91, respectively (Table 2). This indicates that the model structure of Thaumatin100 ms was better fitted into the electron density map than that of Thaumatin18. The thaumatin structure consists of three domains: the flattened \(\beta\)-sandwich domain (Ala1-Thr54, Thr85-Ala127, and Pro178-Ala207), a small disulfide-rich domain (Asp55-Pro84), and a large disulfide-rich domain (Ala128-Cys177) (Figure 4A), which is similar to the findings of a previous report [30]. The superimposition of Thaumatin18 and Thaumatin100 ms showed an r.m.s. deviation of 0.033 A, indicating that the X-ray dose is not critical in changing the main chain conformation of thaumatin. The average temperature factors of Thaumatin18 and Thaumatin100 ms were 10.39 and 13.41 A\({}^{2}\), respectively (Table 2). B-factor putty representation showed that several loop regions of Thaumatin18 were relatively more flexible than those of Thaumatin100 ms (Figure 4B). A normalized B-factor plot showed that loop regions containing Asp60, Arg119, Lys163, and Lys187 of Thaumatin18 showed high B-factor values when compared with Thaumatin100 ms (Figure 4C). \begin{table}
\begin{tabular}{c c c} \hline
**Refinement** & **Thaumatin18** & **Thaumatin100 ms** \\ \hline Resolution range (Å) & 50.0–1.13 (1.17–1.13) & 45.91–1.13 (1.17–1.13) \\ \(R_{\text{work}}\) & 0.1836 (0.3339) & 0.1698 (0.3541) \\ \(R_{\text{free}}\) & 0.1924 (0.3504) & 0.1805 (0.3558) \\ CC (work) & 0.962 (0.739) & 0.971 (0.810) \\ CC (free) & 0.965 (0.690) & 0.957 (0.830) \\ No. of non-H atoms & & \\ Protein & 1583 & 1583 \\ Ligand & 34 & 34 \\ Water & 315 & 332 \\ R.m.s. deviations & & \\ Bonds (Å) & 0.008 & 0.006 \\ Angles (\({}^{\circ}\)) & 0.998 & 0.960 \\ Average \(B\) factors (Å\({}^{2}\)) & & \\ Protein & 10.39 & 13.63 \\ Water & 23.80 & 27.01 \\ Other & 14.20 & 15.69 \\ Ramachandran plot & & \\ Most favored (\%) & 98.05 & 99.02 \\ Allowed (\%) & 1.95 & 0.98 \\ \hline \end{tabular} Values for the outer shell are given in parentheses. \({}^{\text{a}}\) R\({}_{\text{work}}\) = \(\sum\)1 \(F_{\text{obs}}\) = \(\sum\)1 \(F_{\text{obs}}\) \(\mid\) - \(\mid\)\(F_{\text{calc}}\) \(\mid\) 1 / \(\sum\)\(F_{\text{obs}}\) 1, where \(F_{\text{obs}}\) and \(F_{\text{calc}}\) are the observed and calculated structure-factor amplitudes, respectively. \({}^{\text{b}}\) R\({}_{\text{free}}\) was calculated as R\({}_{\text{work}}\) using a randomly selected subset (10%) of unique reflections not used for structure refinement.  
\end{table} 
Table 2: Data refinement statistics. In macromolecular crystallography, the integrity of disulfide bonds and loss of definition of the carboxyl groups of acidic residues are considered a marker for specific radiation damage [12; 31]. Thaumatin has eight disulfide bonds in the \(\beta\)-sandwich (Cys9-Cys204 and Cys121-Cys193), small disulfide-rich (Cys56-Cys66 and Cys71-Cys77), and large disulfide-rich (C126-C177, C134-C145, Cys149-Cys158, and Cys159-Cys164) domains. To identify the specific radiation damage, electron density maps of all disulfide bond regions of Thaumatin [18] and Thaumatin\({}^{100\mathrm{ms}}\) were investigated. In Thaumatin\({}^{18}\), a negative mFo-DFc electron density map appeared at all positions corresponding to sulfur at all disulfide bond positions (Figure 5A). On the other hand, in C9-C204, C56-C66, and C126-C177, a positive mFo-DFc electron density amp appeared in the opposite direction of the disulfide bond position, whereas in C71, C134, and C158, positive mFo-DFc density maps appeared.