Exercise PMF2: Answers

1. What can we learn from this result?

   Real-life samples often show signs of contamination. In this case, the contaminant is human keratin. Could equally well be sheep keratin (from a sweater), bovine trypsin (used for the digest), BSA (blocking the blotting membrane), etc., etc.

2. What advice would you give to the person who ran the spectrum?

   Calibrate your instrument! The data have a precision of better than +/- 25ppm, but the accuracy is ten times worse

   

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