PTM Force Fields (PTMFF). Post-translational modifications (PTMs) are chemical modifications of proteins that are critically important in regulating a protein’s structure and function.10 There are more than 400 types of PTMs that affect more than 70% of proteins. However, the widely-used software packages for biomolecular simulations only have force field parameters for the standard and a limited number of non-standard amino acid residues. We are now developing a PTM force field (PTMFF) that covers the common PTMs (phosphorylation, acetylation, methylation, glycosylation, etc.) and is totally compatible with the existing biomolecular force fields. The PTMFF will be validated by studying the structures, functions, and dynamics of PTM decorated proteins through MD simulations. We are developing PTMFF following the canonical AMBER force field development strategy. A web toolkit deploying PTMFF is accessible by click DPTMFF Database