Nonetheless, SPICA has demonstrated the ability to accurately describe protein assemblies in viral capsids. It was applied to the poliovirus, an icosahedral capsid consisting of 60 copies each of four proteins (VP1, VP2, VP3, and VP4). The CG simulation, initialized from an equilibrated AA structure and incorporating the intrachain EN bonds, maintained a stable capsid over a 1 𝜇s simulation. The average capsid radius was 132.8 Å, closely aligning with the 133.6 Å observed in AA-MD . In the latest version of SPICA version 2 (85), several improvements were made to better model protein-lipid interactions and IDP systems. The previous version tends to over-stabilized protein adsorption on lipid membranes, causing soluble proteins to bind too tightly. To address this, the Lennard-Jones (LJ) parameters for BB-lipid interactions were modified to better reproduce protein binding sensitivity. SPICA 2 was tested on several proteins: lysozyme, phospholipase A2 (PLA2), the pleckstrin homology (PH) domain of PDK1, and the human micelle-bound 𝛼-synuclein (a-syn). Notably, 𝛼-syn chain remains in the For IDP systems, the removal of the EN model, the introduction of secondary structure-dependent nonbonded interaction parameters for the protein backbone, and the re-optimization of nonbonded parameters for all amino acids allow SPICA to accurately model the radius of gyration of IDPs, the free energy of peptide association in water, and specific interactions between lipids and transmembrane proteins. The latest CG potential parameters can be obtained from the webpage (). Currently SPICA does not yet support post-translational modifications (PTMs) and thus their effect on protein conformation remains elusive.