Mass Spectrometry of Intracellular and Membrane Proteins Using Cleavable Detergents

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Abstract
Detergents have been used to enhance the solubility of hydrophobic biomolecules for decades. Despite the widespread use of detergents in biochemistry, the presence of these molecules often complicates further analysis by mass spectrometry. This study presents a solution to this problem by outlining a method utilizing a novel cleavable detergent, 3-[3-(1,1-bisalkyloxyethyl)pyridin-1-yl]propane-1-sulfonate (PPS). This detergent can be used to extract protein contained within the interior of the cell by disrupting cell membranes. Once the proteins are free from the cell, PPS also assists in protein solubilization by shielding the hydrophobic regions of the newly extracted protein from unfavorable interactions with water. The added advantage of PPS over conventional detergents such as sodium dodecyl sulfate or n-octylglucoside is that the detergent properties that interfere with MALDI mass spectrometry can be eliminated prior to analysis. PPS was found to improve sensitivity in MALDI analyses of both soluble proteins and membrane proteins without degrading spectral quality. The virtues of this strategy were applied to whole cell extracts. Analysis of these extracts resulted in an overall increase in both the number of peaks observed and overall signal intensity.