Mascot: The trusted reference standard for protein identification by mass spectrometry for 25 years

Exercise SQ2


A trickier sequence tag search


User access to any Mascot server, including the Matrix Science public web site


The sample was digested with trypsin and analysed on an ESI-QUAD-TOF. A tag has been interpreted from one of the MS/MS spectra. Precursor m/z is 703.74 with charge 2+. The low mass end of the tag starts at m/z 147.07. Residue code i means I or L. Search Swiss-Prot with precursor and fragment mass tolerances of 0.5 Da

sequence tag


  • If you cannot get a match with a standard tag, try an error tolerant tag


  1. What is the peptide sequence?
  2. Are there any alternative solutions?
  3. If so, how do you choose a preferred solution?


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