Summary of peptides in E. coli MC4100, in which cysteines were found to be substituted by selenocysteine and dehydroalanine by ESI-LTQ-Orbitrap-MS/MS.

Charge states of precursor ions that were selected for MS/MS analysis are indicated. *1: C: cysteine; c: carbamidomethylated cysteine; u: carbamidomethylated selenocysteine; a: dehydroalanine; selenocysteine at position 196 is the naturally occurring amino acid. *2 Two complementary protein purifications were performed from MC4100 cells cultivated with different concentrations of the trace elements selenium and molybdenum. Cultures were supplemented with 2 µM or 100 µM of sodium selenite and sodium molybdate, respectively.