## 4 Discussion
The behavior of this variable over time for all the complexes studied is shown in Figure 11. As can be seen in Figure 2, all complexes subjected to molecular dynamics simulations maintained low RMSD values (<2 A), indicating that these complexes remained stable throughout the simulation period. This result is consistent with that obtained from the docking experiments. The lowest RMSD values were found in the complex formed by Benztropine and the dopamine receptor, meaning that it was the most stable complex over time. This complex had the most negative energy obtained in the docking experiments, coinciding with the results obtained from the docking experiments and the molecular dynamics experiments; therefore, we can expect that this molecule could be a good candidate as a radiotracer for [PERSON]'s disease diagnosis. One of the parameters that could explain the stability of compounds over time is hydrogen bond interactions (Figure 12). As can be seen in Figure 12, the number of hydrogen bond interactions during the trajectory was low. The highest number of hydrogen bond interactions was found in the complex formed by Procaine and the dopamine transporter. Given the structure of this molecule (Figure 3), there is only one possibility of hydrogen bond interaction as the hydrogen acceptor: the carbonyl oxygen of this ligand, which  
Figure 10: Graphical representation of the ligands with the lowest binding energy calculated in the docking experiments at the dopamine transporter pocket. interacts strongly and stably with Asp79 of the dopamine transporter with an occupancy of 88.81% (Table 7). This interaction could give the complex strong stability during the simulation time. The second complex with stable hydrogen bond interactions over time was found in the complex formed by diethylpropion with the dopamine transporter. This complex maintained strong interactions with Asp421 with an occupancy of 60.98% (Table 7), which is considered a stable interaction over time. This behavior could explain the low RMSD values found during the 100 ns trajectory. In the case of the complex formed by Benztropine and the dopamine transporter, no stable hydrogen bond interactions were found over time. Given the structure of this \begin{table}
\begin{tabular}{c c c} \hline \hline
**Complexes** & **H-Bond Interaction** & **Occupancy (\%)** \\ \hline Diethylpropion-8Y2D & ASP421-Side & 60.98\% \\  & PHE320-Main & 15.76\% \\  & ASP79-Side & 88.81\% \\  & VAL78-Main & 15.16\% \\  & LEU459-Main & 0.08\% \\  & ASP231-Side & 0.04\% \\ \hline \hline \end{tabular}
\end{table} 
Table 7: H-bond occupancies analysis during 100 ns of simulation time. Figure 11: Behavior of the RMSD parameter during the 100 ns of simulation time. Figure 12: Radius of gyration of the alpha carbon of the protein in complex with the studied molecules during 100 ns of simulation time. molecule (Figure 11), it has little chance of interacting by hydrogen bond with the amino acids of the dopamine transporter, because it only has one hydrogen acceptor group and it is an oxygen of the ether group within Benztropine. The stability of this complex found in the RMSD parameter could be because of another type of interaction such as \(\pi\)-\(\pi\) staking, Van del Waals interactions, or solvation type. Another parameter usually used to analyze ligand-protein complexes is the radius of gyration. This variable provides information about the degree of compaction of a complex during the simulation time. As can be seen in Figure 12, the two most compact complexes were those formed by Proocaine and Benztropine, with radii of gyration values below 4 A. This result is consistent with the RMSD results and with the results obtained from the docking experiments, so we can conclude that these two compounds could be good markers for [PERSON]'s disease.