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

Exercise MSMS7

Topic

High precursor accuracy

Requirements

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

Experimental

Proteins from human serum analysed on an FT instrument. Cysteine residues reduced and alkylated with iodoacetamide (+57). Can use precursor tolerance of 5 ppm and fragment tolerance of 0.2 Da. Trypsin with 2 missed cleavages. Quite a lot of oxidised Methionine and many cases where peak picking has taken the 13C peak instead of the 12C peak.

Data

Right-click this link: MSMS7.mgf, and choose Save target as or Save link as

Questions

  1. How can you distinguish between peak picking choosing the 13C peak and deamidation?
  2. Is there evidence of non-specific cleavage?

 

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