Recent studies using stable isotope labeling with amino acids in culture (SILAC) in
quantitative proteomics have made mention of the problematic conversion of isotope-coded
arginine to proline in cells. The resulting converted proline peptide divides the heavy
peptide ion signal causing inaccuracy when compared with the light peptide ion signal. This
is of particular concern as it can effect up to half of all peptides in a proteomic experiment.
Strategies to both compensate for and limit the inadvertent conversion have been …