A sucrose cushion is a technique used in laboratory settings, specifically in biochemistry and molecular biology, to isolate or purify particles, such as viruses or cellular organelles, from a sample.

A sucrose cushion involves layering a high concentration sucrose solution at the bottom of a centrifuge tube. The sample containing the particles of interest is then carefully layered on top of the sucrose cushion. When the tube is centrifuged, the particles in the sample are sedimented through the sucrose cushion, which acts as a density gradient, allowing for separation and purification.

The sucrose cushion technique takes advantage of the different densities of the particles and their buoyancy in the sucrose solution. The particles with densities similar to the sucrose cushion will float at their respective positions within the cushion, while other components of the sample will be separated and can be removed. This allows for the enrichment and isolation of specific particles or organelles for further analysis or experimentation.