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Exercise MSMS7


High precursor accuracy


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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.


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  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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