Add reference The submitted dataset contains raw files from 96 synthetic peptide libraries, using either HCD or ETD as fragmentation technique. The synthesized 96 tryptic peptide libraries containing >100,000 unmodified peptides plus their corresponding >100,000 phosphorylated counterparts with precisely known sequences and modification sites. All these libraries were subjected to LC-MS/MS on an Orbitrap mass spectrometer using HCD and ETD fragmentation. The generated mass spectrometric data deposited in this database can be used in numerous ways to develop, evaluate and improve experimental and computational proteomic strategies. Raw MS data files were converted into Mascot generic format files (MGF) using Mascot Distiller (2.4.2.0, www.matrixscience.com). Important parameters included: i) signal to noise ratio of 20 for MS/MS and ii) time domain off (no merging of spectra of the same precursor). The MGF files were searched against human IPI v3.72 including the sequences of all 96 libraries,using the Mascot search engine (2.3.1, 24). Search settings: Decoy search using a randomized version of the human IPI v3.72 including the sequences of all 96 libraries was enabled; monoisotopic peptide mass (considering up to two 13C isotopes); trypsin/P as protease; a maximum of four missed cleavages; peptide charge +2 and +3; peptide tol. +/- 5 ppm; MS/MS tol. +/- 0.02 Da; instrument type ESI-Trap (for HCD data) or ETD-Trap (for ETD data) respectively; variable modifications: oxidation (M), phospho (ST), phospho (Y). The result files were exported to pepXML and Mascot XML with default options provided by Mascot.