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Membrane protein extraction with detergents and chaotropes solubilizes lipid-bilayer-associated proteins by disrupting protein-lipid and protein-protein interactions while maintaining proteins in a soluble state for downstream electrophoresis, purification, or mass spectrometry. Chaotropes such as urea and thiourea improve solubilization of difficult proteins, while nonionic and zwitterionic detergents such as CHAPS, ASB-14, SB 3-10, MEGA-10, dodecyl maltoside, and Triton X-100 differ in extraction efficiency depending on sample type and membrane protein properties.

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.