SEQUEST and XTandem! are proteomic search engines designed to match experimental spectra to theoretical spectra.Use the help information for each of these resources to determine the parameters each of these programs use to validate a spectral match. For example describe how XCorr and delta Cn are computed. How can XCorr or delta Cn be used to validate spectral matches? Which statistical parameters are used by XTandem! to validate spectral matches? How does XTandem! compare to SEQUEST?