Removal of NHS-labelling by-products in proteomic samples

N-Hydroxysuccinimide chemistry is used extensively across proteomics sample preparation. One of the most popular applications is its use in isobaric reagent based quantitation; specifically both the iTRAQ and TMT approaches which rely on complete labelling of primary amines. However, serines, tyrosines and threonines can also react during TMT labelling procedures. These products are typically classed as over-labelled and are disregarded for quantification. In this study we developed a robust method to remove such over-labelled peptides to improve identification rates and quantitation precision and tested the new method or compatibility with phoshpo-peptides.