Figure 2.

Schematic overview of quantitative proteomics methods discussed in this paper. (a) Workflow of enrichment methods used in ubiquitin-profiling proteomics based on anti-ubiquitin (Ub) immunoprecipitation (left), ubiquitin pull down with selective ubiquitin-binding domain reagents (TUBEs, middle) and tryptic ubiquitin remnant peptide antibody immunoprecipitation (right). (b) Workflow of methods for enriching N-terminal peptides by chemical labelling of primary amines followed by removing non-labelled peptides via binding to an aldehyde-functionalized polymer (TAILS, left), chemical labelling of primary amines and sequential chromatographic fractionation to enrich for N-termini (COFRADIC), and enzymatic labelling of N-terminal α-amines and subsequent pull down of labelled peptides (right). (Online version in colour.)