Removal of sodium dodecyl sulfate from protein and peptide samples with cross-linked [Os(dmebpy)_2Cl]^(+/2+)-derivatized acrylamide and vinylimidazole copolymer

Abstract

Rationale Sodium dodecyl sulfate (SDS) is widely used for the solubilization and denaturation of proteins, but it interferes with liquid chromatography/mass spectrometry (LC/MS), suppressing protein signals or forming adduct ions. A quick and effective clean-up technique of SDS is essential for MS analysis of proteins. Ion-exchange spin columns are commonly used for SDS removal in protein samples. Methods A bulk sample of insoluble, cross-linked [Os(dimethylbipyridine)_2Cl]^(+/2+)-derivatized poly(acrylamide)-poly(vinylimidazole) copolymer was synthesized and broken into small particles. The polymer was activated by washing with 1:1 ACN/water 50 mM triethylammonium phosphate 0.05% TFA, 0.1% TFA ACN and then 0.1% TFA water. Under acidic aqueous conditions, SDS adsorbs on the activated surfaces of the Os-complexed copolymer particles, but not the proteins and peptides in the same mixtures. Thus, the copolymer can be used to remove SDS from protein and peptide samples. The copolymer-adsorbed SDS is removed by washing with 0.1% TFA ACN, permitting re-use of the copolymer. Results Standard myoglobin and some practical protein samples from a biochemistry lab spiked with different concentrations of SDS were successfully cleaned up using this Os-copolymer for LC/MS analyses. Up to 0.2% (w/v %) of SDS can be successfully removed from those protein samples. Conclusions This Os-complexed copolymer provides a new alternative for quick cleanup of SDS from protein samples, and can serve as a new class of metal complex based anion exchanger for protein purification.

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