Abstract: 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.

Abstract: The present invention describes a method that combines the blocking of primary amino groups and the cation exchange chromatography, to simplify peptide mixtures that can be generated or not by proteolytic or chemical treatments. This method allows the selective isolation of an average of 4 multiply-charged peptides (RH peptides) per protein and the study of 90% of the proteins of the analyzed proteomes. It is applicable to studies of quantitative proteomics without the usage of two-dimensional electrophorsis, it is compatible with any type of isotopic labeling and it is very useful to determine the differential expression of proteins present in multiple conditions (3 to 6 conditions) when using different isotopic labeling in a single experiment. The chromatographic system used also allows the fractionation fraction of the RH peptides to achieve the identification of a greater number of proteins.