Fig. 2. A schematic representation of the raft flotation assay. The plasma membrane (blue) contains lipid rafts (brown). Rafts contain proteins (men) with affinity for their particular lipid composition. The bulk phase of the plasma membrane also contains membrane proteins (ducks). Fish indicate cytoplasmic proteins. Homogenization leads to the formation of membrane vesicles. Cold Triton X-100 treatment solubilizes the bulk phase of the plasma membrane, but the raft domains remain insoluble. The raft fraction floats upon centrifugation from the bottom of a sucrose gradient, whereas cytoplasmic and dissolved plasma membrane proteins remain at the bottom of the tube.

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