Sodium dodecyl sulfate removal during electrospray ionization using cyclodextrins as simple sample solution additive for improved mass spectrometric detection of peptides
Quirino, JP, Sodium dodecyl sulfate removal during electrospray ionization using cyclodextrins as simple sample solution additive for improved mass spectrometric detection of peptides, Analytica Chimica Acta: International Journal Devoted to All Branches of Analytical Chemistry, 1005 pp. 54-60. ISSN 0003-2670 (2018) [Refereed Article]
Sodium dodecyl sulfate (SDS) removal is a vital procedure in SDS-assisted bottom-up proteomics because SDS affects the quality of the data in electrospray ionization mass spectrometry (ESI-MS). SDS removal methods provide efficient removal of SDS and improved peptide analysis, but would usually require time, specialised devices, and experienced analysts. Here, by simple addition of γ-cyclodextrin (γ-CD) to the solution at concentrations 1 to 2x the SDS in the sample, the SDS related signals in positive ionization ESI-MS can be significantly removed (70–99% reduction), without an additional sample manipulation step of extraction or purification. The mechanism for removal is based on the formation of tightly bound CD-SDS inclusion complexes, which hampered the generation of positively charged SDS multimers during ESI. For a sample with peptides (glu-val-phe, tyr-tyr-tyr, and bradykinin) and 3 mM SDS where 6 mM γ-CD was added, the %signal recoveries of peptides calculated by comparison with signals from standard samples without SDS were 49–59%. The space charge effect by SDS on bradykinin was also reduced, increasing the signal for bradykinin 12x in the presence of γ-CD. For a protein (bovine serum albumin, BSA) digest with 3 mM SDS, which is an expected concentration in trypsin treated samples, a noticeable 7-fold improvement in the peptide to SDS signal ratio and a 91% reduction of SDS signals were observed upon addition of 6 mM γ-CD. However, there were only small changes in the ESI-MS intensities for the BSA peptides (compared to without addition of γ-CD). This new approach to SDS signal removal using CDs in ESI-MS may find use in proteomic studies.