The benefits (and misfortunes) of SDS in top-down proteomics

Top-down proteomics (TDP) has great potential for high throughput proteoform characterization. With significant advances in mass spectrometry (MS) instrumentation permitting tandem MS of large intact proteins, a limitation to the widespread adoption of TDP still resides on front-end sample preparation protocols (e.g. fractionation, purification) that are amenable to MS analysis of intact proteins. Chromatographic strategies are improving but pose higher risk of sample loss. Gel-based separations (e.g. GELFrEE) may alleviate this concern but at the expense of requiring sodium dodecyl sulfate (SDS). While this surfactant maintains protein solubility during fractionation, the advantage is short-lived, as the detergent must ultimately be depleted to avoid MS signal suppression. To do so requires overcoming strong interactions between SDS and protein. Adding to the challenge, one must now consider upholding the solubility of purified protein(s) in the absence of SDS. This review explores uses of SDS in TDP workflows, addressing front-end strategies that reduce matrix interferences while maximizing recovery of intact proteins in MS-compatible formats.

The benefits of employing SDS in a TPD workflow can easily outweigh the disadvantages. Several SDS depletion strategies are available, though not all are equally amenable to TDP. This review provides a comprehensive and critical accounting of SDS in TDP, demonstrating methods that are suited to MS analysis of intact proteins.