## 3 Results and Discussion
### Molecular Dynamics Simulation  
The properties and interactions of the Am1 Gly complex with ER\(\alpha\) were observed using molecular dynamics simulations. Under specific pressure and temperature settings, the ligand-receptor complex was observed over a duration of 200 ns [58]. In addition, molecular dynamic simulations of the 4-hydroxytamoxifen-ER complex were performed to aid in the comparison of antagonist complex properties with those in previous studies [36; 59]. The molecular dynamics simulation of Am1 Gly was carried out for 200 ns using AMBER22, and the results were analyzed using RMSD and RMSF charts [60]. The ligand-ER\(\alpha\) interaction was parameterized using the ff14 SB, GAFF, and AM1-BCC force fields [59]. The average distance that atoms traveled away from the reference structure is shown by the RMSD value. The Er\(\alpha\)-Am1 Gly combination reached stability around frame 2000, with an RMSD value similar to that of the ER\(\alpha\)-4-hydroxytamoxifen complex. The ER\(\alpha\)-Am1 Gly complex demonstrated a slight stability in comparison to the ER\(\alpha\)-4-hydroxytamoxifen complex (Figure 8). The RMSD values for Am1 Gly and 4 OHT are similar, measuring around 0-2 A. The ER\(\alpha\) receptor's flexibility is stable when interacting with Am1 Gly and 4 OHT, as the protein remains folded and does not alter significantly during dynamic simulations [61]. Figure 8: Am1 Gly and 4-hydroxytamoxifen’s RMSD plot vs. ER\(\alpha\). Figure 7: The molecular interaction of Am1 Gly with the ER\(\alpha\) receptor showed essential hydrogen bonds (green lines) and hydrophobic interactions (pink lines). The RMSF analysis establishes the stability pattern in order to study changes in protein and amino acid composition that occur during the interaction of the Am1 Gly and 4 OHT complexes [62]. RMSF focuses on the protein's complex region and the fluctuating amino acid residues throughout its structure. During the MD simulations, higher RMSF values reflect weaker stability and greater flexibility, while a lesser RMSF amplitude shows strong consistency for ligand complexes [63]. The RMSF analysis (Figure 9) shows quite similar residual fluctuations between Am1 Gly and 4-hydroxytamoxifen. Pro333, Thr334, Arg335, Cys417, Ser464, Lys531, and Pro552 were among the residues that exhibited changes as a result of Am1 Gly and 4 OHT. The ER\(\alpha\) protein's structure includes a hydrogen bond network between Glu419, His524, and Lys531. This network ensures Helix-3 and Helix-11 of ER\(\alpha\) maintain tight touch [64]. If a ligand disrupts the hydrogen bond through fluctuations, it can act as an antagonist to the ER\(\alpha\) receptor [65]. Am1 Gly and 4 OHT damage the hydrogen bond by causing variations between Ser432 and Ser521. This suggests that Am1 Gly may have anti-ER\(\alpha\) properties. The hydrogen bond analysis results indicate that Am1 Gly has the majority of its hydrogen bond interactions with residue Asp351 (49.80% occupancy), Phe404 (12.85% occupancy), and Glu353 (4.87% occupancy) (Table 3). These interactions differ significantly from those of 4 OHT. Despite the difference in the occupancy of amino acid residues between 4 OHT and Am1 Gly, especially the Asp351 residue, it can still be inferred that the Am1 Gly compound may act as an antagonist to ER\(\alpha\). This inference is supported by the results of molecular dynamics by [PERSON] et al., which show that Am1 Gly exhibits important hydrogen interactions with residues Asp351, Arg394, and Glu353, which are stabilizing interactions characteristic of an ER\(\alpha\) antagonist [59, 66, 67]. These findings, drawn from both molecular docking and dynamics data, suggest that Am1 Gly is necessary for ER\(\alpha\) antagonistic activity. This also suggests that Am1 Gly may have a similar antagonistic ER\(\alpha\) action to 4 OHT. The binding energy was then computed using the MMPBSA method to predict the binding affinity of Am1 Gly against ER\(\alpha\). The MMPBSA approach is regarded as more advanced for calculating binding free energy [68].