Reconstructed ion chromatograms of oxidized tryptic fragments. (A) In the presence of 75μM HOCl, approximately 99% of the A2 peptide contained methionine sulfoxide at position 1606, whereas only 0.3% contained both chlorotyrosine at position 1605 and methionine sulfoxide at 1606. (B) The content of methionine sulfoxide at position 1606 increased with increasing concentration of HOCl.