Method for the identification and relative quantification of proteins based on the selective isolation of RRnK peptides for the simplification of complex mixtures of proteins

A method based on the selective isolation of peptides originated by the cleavage at the C-terminal end of the arginine residues and do not possess lysine inside their sequences (péptidos RRnK), is described. The method is based on the blocking of amino groups of the LEP peptides and the separation of the RRnK peptides and the modified peptides by using a chromatography column or a chemical reaction of the modified peptides with a solid support. The method simplifies the complex mixtures of peptides by isolating selectively an average of 4 peptides/protein and it guarantees a coverage of 88% of the proteomes, its specificity and selectivity are very high (>95%), it is compatible with different types of isotopic labeling (13C, 18O or 15N) and it is useful for the determination of the differential expression of proteins without the necessity of using the two-dimensional electrophoresis.