1. A Method for the determination of an SRM assay for the detection and/or quantification of one or more peptides and/or proteins including the following steps: (1) preparation of a mixture of peptides in that a protein/peptide of interest, a group of proteins/peptides of interest, a subproteome or a whole proteome, is cleaved and/or digested, optionally followed by purification/separation/enrichment, to form said mixture of peptides, unique association at least one peptide of the protein of interest or a target protein of said group of proteins of interest or of said whole proteome from said mixture in a mass spectrometry experiment, wherein it is associated in terms of differential quantitative behaviour under different experimental conditions; (2) synthesis or generation of this at least one peptide essentially without subsequent purification; (3) analysis of this at least one unpurified peptide by selected reaction monitoring, or liquid-chromatography-coupled selected reaction monitoring; (4) development, validation and/or optimisation of the corresponding assay of the at least one peptide with determination of the SRM coordinates for a peptide/protein of interest and/or of a regulator of interest.