... [13C]methionine or[12C]methionine. With COFRADIC, we sort for methi-onine-containing peptides only: thus, we select out of the mixture only those peptides containing the differ-ential information, ... reached. Incontrast, using COFRADIC, we select subsets of pep-tides related to the biological question under investiga-tion. For instance, for the study of the oxidation of protein methionines during ... the part of a proteomecontaining the information of biological interest. Ourtechnique is based on diagonal chromatography [30,31]consisting of two repeated, identical peptide separa-tions with...