This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Posttranslational modifications (PTMs) play essential roles in protein function and cellular physiology. Unrestrictive identification of all types of PTMs using mass spectrometry is a powerful approach. Previous efforts have allowed us to successfully develop PTMap v2.0, a tool for genome-wide characterization of protein posttranslational modifications. Initial tests demonstrate that PTMap2 is capable to identify all types of PTMs in E. coli protein database from a single mass spectrometry data file. Here we propose to extend the application of PTMap2 tool to identify unknown PTMs in diverse cellular organisms.