The Partial Mammalian Proteome Extraction Kit (P-PEK, Mammalian) is designed for serial sample preparation of complex mixtures using reagents with increasing solubilization strength. Each of the provided extraction reagents solubilizes a different subset of cell proteins. The most soluble of the mammalian proteins are released by mechanical destruction of the cells in Extraction Reagent 1, proteins of intermediate solubility are subsequently extracted with reagent 2, then the membrane proteins can be extracted using Extraction Reagent 3. These fractions can then be analyzed on separate 2-D gel electrophoresis and the insoluble fraction can be analyzed by one-dimensional SDS-PAGE using the SDS buffers provided. To preserve the protein profile and increase spot resolution, the kit also contains Protease Inhibitor Cocktail and the proprietary non-specific nuclease, Benzonase^® Nuclease (Cat. No. 71206). Sample size: 1-2x10⁸ cells or 500 mg tissue.