Comparison of sodium dodecyl sulfate depletion techniques for proteome analysis by mass spectrometry

Carolyn Kachuk, Kegan Stephen, Alan Doucette

Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada.

Abstract

In proteomics, sodium dodecyl sulfate (SDS) is favored for protein solubilization and mass-based separation (e.g. GELFrEE or SDS PAGE). Numerous SDS depletion techniques are available to purify proteins ahead of mass spectrometry. The effectiveness of the purification has a controlling influence on the success of the analysis. Here we quantitatively assess eight approaches to SDS depletion: in-gel digestion; protein precipitation in acetone or with TCA; detergent precipitation with KCl; strong cation exchange; protein level and peptide level purification with Pierce detergent removal cartridges; and FASP II. Considering protein purity, FASP II showed the highest degree of SDS removal, matching that of in-gel digestion (over 99.99% depleted). Other methods (acetone, strong cation exchange, Pierce cartridges) also deplete SDS to levels amenable to LC–MS (>99%). Accounting for protein recovery, FASP II revealed significant sample loss (<40% yield); other approaches show even greater protein loss. We further assessed acetone precipitation, having the highest protein recovery relative to FASP II, to process GELFrEE fractionated Escherichia coli ahead of bottom-up mass spectrometry. Acetone precipitation yielded a 17% average increase in identified proteins, and 40% increase in peptides, indicating this approach as a favored strategy for SDS depletion in a proteomics workflow.

Keywords: SDS depletion; Proteomics; Protein recovery; Protein purification; Acetone precipitation; FASP II.