For the SARS-CoV-2 spike protein receptor-binding domain (RBD), a 1.8 ms-long MD trajectory starting from an experimental structure (PDB: 6M0J) is publicly available. Given the availability of this long MD simulation, time-lagged independent component analysis (TICA) was a natural choice to project the structures into a 2D space for visualization. Using a time lag of 10 ns, we computed the free energy in this space, revealing four distinct basins (background topology in Figure ; see Supplementary Methods).