## 3 Results and Discussions
### Solvent Accessible Surface Area (SASA) Analysis  
The previous article explored the formation of more hydrogen bonds between the hydrogen bond breaks inside the protein and the water molecule under the action of the electric field and found that the contact area between the protein and the water may change during the reaction. To explore the interaction between proteins and solvents, we continued to study the SASA of proteins to analyze changes in the protein-water contact area. We performed this by calculating the contact area change chart between the No. 4H9\(W\) protein and the three-segment residue (residues 61-88, residues 139-149, residues 169-180) and the water solvent, as shown in Figure 9. As can be seen from Figure 9a, the SASA value of the protein of the reference group (310 K, 0 v/nm) of this experiment was stable at about 100 nm\({}^{2}\) without significant change, which proves that the protein has a certain force inside, so that it can maintain structural stability in the natural state and, thus, stabilize the contact area with water. Under the action of the electric field, the contact area of the protein as a whole with the water solvent increases sharply, and it is dynamically balanced at a certain value after 25 ns. It can be seen that the internal structure of the protein changes significantly under the action of the external electric field, and some areas become stretched or rotated from curling up to expanding so that the contact area with the water solvent increases. Since most of them are distributed on the surface of the protein, more active sites are exposed [36]. In addition, as the strength of the combined electric field increases, the change time of the contact area is significantly shortened, and the area growth rate increases significantly, which also matches the results of the previous analysis of the RMSD, dipole moment, and hydrogen bond. In combination with the protein RMSD curve in Figure 2a, it is not difficult to find that the curves of different parameters under the same electric field change at the same speed. Taking the electric field of 0.5 v/nm applied simultaneously in the x, y, and z axes as an example, the RMSD and SASA parameter curves of the proteins both increased to the highest within 10 ns after the simulation began and then tended to be stable. Figure 9b-d calculates the SASA values of residues 61-88, 139-149, and 169-180, respectively, and we found that the SASA parameter changes in some protein fragments were slightly different from the overall characteristics discussed above. Taking residues 61-88 as an example, we could see that the contact surface of this segment of the residue with the aqueous solvent mostly significantly increased after different electric fields were  
Figure 8: The curves of the number of hydrogen bonds between residues 169 and 180 and water under different amounts and directional electric fields. Figure 7: The change curves of the number of hydrogen bonds between residues 139 and 149 and water under different amounts and directional electric fields. applied, indicating that the deformation of this protein fragment under the action of the electric field exposed more hydrophilic regions. In particular, when an electric field of 0.354 v/nm was applied simultaneously in the x, y-axis direction, the SASA value of this fragment dropped to a certain extent before it began to grow and exceed the reference value, indicating that residues 61-88 in this state may shrink to a certain extent and then expand. In the RMSD and hydrogen bond parameter curves of residues 139-149, the parameters in this direction electric field were the most active. By observing Figure 9c, it can be found that the SASA change in residues 139-149 under the action of the electric field is not drastic, and the same change in the number of hydrogen bonds is also the overall upward movement of the curve, which proves that the conformational change in this protein fragment is not clear.