Cell fractionation

Cell fractionation below refers to the isolation ( separation) of the components of a cell according to the cell information, for example, organelles and cytosolic proteins.

The cell fractionation is usually carried out by centrifugation, whereby fragments of the cell membrane and nuclei sedimented first, followed by the mitochondria, the endoplasmic reticulum, and in the supernatant remain cytosolic proteins. With careful work, the cell organelles remain intact and largely functional. After cell disruption, the cell components are present in a " porridge -like" state. The cell fractionation is often just the beginning of a protein purification, a DNA or an RNA isolation dar.

Methods

Density

In density, the homogenate is applied to the surface of a density gradient and then centrifuged. Now the cell components have joined to their respective density zone. It makes sense this procedure if you want to isolate cell components of similar size with a small density difference.

Differential centrifugation

The differential centrifugation is a separation process, in which the cellular components are separated by a plurality of serial centrifugations at higher and higher speeds. It makes use of the fact that centrifugation unravel cellular components based on their size and density. Large and dense components migrate it the fastest, so sit down since at relatively low speeds and form a pellet.

A cell homogenate is centrifuged at low speed ( 1 ). The pellet formed (green) consists of large, heavy parts. The supernatant is removed and centrifuged at a somewhat higher speed ( 2 ). This operation is repeated and increased speed at each centrifugation. For the separation of cellular components, the following rules of thumb apply: Nuclei in sediment centrifugation at 1000 g for 5 - 10 min; Mitochondria with 10,000 g for 15 min, and microsomal at 100,000 g for 1h.