Evaluation of the combinative application of SDS and sodium deoxycholate to the LC-MS-based shotgun analysis of membrane proteomes.

SDS and sodium deoxycholate (SDC) as two representative detergents have been widely used in LC-MS/MS-based shotgun analysis of membrane proteomes. However, some inherent disadvantages limit their applications such as interference with MS analysis or their weak ability to disrupt membranes. To address this, the combinative application of SDS and SDC was developed and evaluated in our study, which comprehensively used the strong ability of SDS to lyse membranes and solubilize hydrophobic membrane proteins, and the high efficiencies of an optimized acetone precipitation method and SDC in sample clean-up, protein recovery, and redissolution and digestion of precipitated proteins. The comparative study using a rat-liver-membrane-enriched sample showed that, compared with other three commonly used methods including the filter-aided sample preparation strategy, the combinative method not only increased the identified number of total proteins, membrane proteins, and integral membrane proteins by an average of 19.8, 23.9, and 24.8%, respectively, but also led to the identification of the highest number of matching peptides. All these results demonstrate that the method yielded better recovery and reliability in the identification of the proteins especially highly hydrophobic integral membrane proteins than the other three methods, and thereby has more potential in shotgun membrane proteomics.