The time-dependent values for RMSD and Rg (Figure S 5-S 7) revealed an increased RMSD and Rg for the vitamin D2 complex compared to the apo structure. In Figure (a), the 2D free energy surface illustrated two energy minima with RMSD values of 0.3 and 0.5 nm, and Rg values of 2.10 and 2.14 nm. An RMSD value of 0.5 nm coupled with an increased Rg value of 2.14 nm suggests reduced stability and compatibility of the complex. Conversely, the complex formed by vitamin D3 exhibited a single free energy minimum at an RMSD value of 0.35 nm and an Rg value of 2.06 nm as shown in Figure (b). The free energy surface indicated a strong complex formation between vitamin D3 and the SIRT1 receptor. These observations contrast with the docking results, which suggested a good affinity for vitamin D2.