Membrane-Free Electrokinetic Device Integrated to Electrospray-Ionization Mass Spectrometry for the Simultaneous Removal of Sodium Dodecyl Sulfate and Enrichment of Peptides

Abstract

The removal of sodium dodecyl sulfate (SDS) in SDS-assisted proteomics with electrospray-ionization-mass-spectrometric (ESI-MS) analysis is an essential step in the analysis. Off-line state-of-the-art sample-preparation strategies can allow 100% removal of DS and up to 100% peptide recoveries. These strategies, however, are typically laborious and require long analysis times and a complex experimental setup. Here, we developed a simple, membrane-free, electrokinetic, on-line, integrated SDS removal-ESI-MS device that was able to enhance ESI-MS signals of bradykinin and peptides from trypsin-digested bovine serum albumin (BSA) in samples that contained SDS micelles. The significant peptide-signal improvements were contributed by the complete removal of DS and the enrichment of the peptides in the presence of an electric field. Enrichment was via micelle-to-solvent stacking, initially developed in capillary electrophoresis. Bradykinin percent recovery was 800%, and BSA peptide percent recovery was 87%. Enhancement factors in ESI-MS signals (after and before removal) for selected m/ z values of peptides from the BSA digest were 535-693.

Challenging Bioanalyses with Capillary Electrophoresis

“…However, derivatization strategies for CE-MS analyses were described. One study reported the means to create a set of cationic metabolites as a result of derivatization with a tertiary amine . This one-pot, two-step derivatization had the benefit of improving the ionization efficiency of negatively charged analytes.…”

“…One study reported the means to create a set of cationic metabolites as a result of derivatization with a tertiary amine. 134 This one-pot, two-step derivatization had the benefit of improving the ionization efficiency of negatively charged analytes. In another publication, a method was developed to derivatize and resolve five D-and L-amino acids, as a strategy to detect D-amino acids in spinal fluid.…”

Automated Electrokinetic Platform for High-Throughput Sodium Dodecyl Sulfate Depletion Ahead of Proteome Analysis by Mass Spectrometry

“…22 Tubaon et al described a semiautomated electrokinetic device for SDS removal from peptides, which collapses detergent micelles at a solvent interface within a customized set of interconnected capillaries. 23 Their process, known as micelle-to-solvent stacking (MSS), 24 concentrates peptides into a narrow zone that is separated from SDS. Direct infusion of peptides spiked with ∼0.1% SDS showed enhanced MS signals following 20 min of focusing, although other contaminant signals were prominent in the spectra.…”

“…Protein purification was achieved in 5 min, although SDS-adducts remained visible in the reported MS spectra of intact proteins . Tubaon et al described a semiautomated electrokinetic device for SDS removal from peptides, which collapses detergent micelles at a solvent interface within a customized set of interconnected capillaries . Their process, known as micelle-to-solvent stacking (MSS), concentrates peptides into a narrow zone that is separated from SDS.…”