of limited specificity. Sequence database searching also demands vast search space, which still could not cover all possibilities of peptide dynamics, exhibiting limited efficiency post-translational modifications). The search process is sometimes slow and requires costly high-performance computers. In addition, the nature of sequence database searching disconnects the research discoveries among different groups or at different times. Advantages and limitations First, a greatly reduced search space will decrease the searching time. Second, by taking full advantage of all spectral features including relative fragment intensities, neutral losses from fragments and various additional specific fragments, the process of spectra searching will be more specific, and it will generally provide better discrimination between true and false matches. Spectral library searching is not applicable in a situation where the discovery of novel peptides or proteins is the goal. Fortunately, more and more high-quality mass spectra are being acquired by the collective contribution of the scientific community, which will continuously expand the coverage of peptide spectral library. Research community focused peptide spectral Libraries For a peptide spectra library, to reach a maximal coverage is a long-term goal, even with the support of scientific community and ever-growing proteomic technologies. However, the optimization for a particular module of the peptide spectra library is a more manageable goal, e.g. the proteins in a particular organelle or relevant to a particular biological phenotype. For example, a researcher studying mitochondrial proteome, will likely focus his/her analyses within protein modules within the mitochondria. The research community focused peptide spectral library supports targeted research in a comprehensive fashion for a particular research community. References External links COPa Library SpectraST Peptides Mass spectrometry software