In order to be able to efficiently purify and analyze proteins, they must first be released from their host cell in a soluble form. Therefore, the first step in protein purification and analysis is cell lysis. Mammalian cells are bounded by a plasma membrane, which is composed of phospholipids and proteins. In contrast to bacterial or yeast cells, this membrane can be easily disrupted, but any lysis method should be gentle enough to deliver active, native-conformation proteins. The Qproteome Mammalian Protein Prep Kit provides gentle but efficient detergent-based lysis of mammalian cells to deliver a total protein fraction suitable for any downstream application. Cell pellets are incubated with Mammalian Cell Lysis Buffer that is supplemented with Benzonase® — an enzyme that digest nucleic acids — and a protease inhibitor, which protect the released proteins from enzymatic degradation. No specialized equipment is required. Cells are simply incubated with lysis buffer and centrifuged to separate cell debris. The supernatant contains the total protein fraction, which can be further purified or directly analyzed, for example by SDS-PAGE.