Cell fractionation is the separation of homogeneous sets, usually organelles, from a heterogeneous population of cells.

Steps

1. Disruption (homogenisation) of cells and liberation of organelles.
2. Macro Filtration
3. Purification of cell components.

Homogenization

Tissue is typically homogenised in an isotonic buffer solution using a variety of mechanisms. A 'Potter-Elvehjem homogeniser' is often used as it is relatively gentle. Other procedures include grinding, mincing, chopping, pressure changes, osmotic shock and freeze-thawing.

The solution is homogenised in an isotonic solution to stop osmotic damage, with a pH buffer to regulate pH, and at an ice-cold temperature to prevent enzyme damage.

Consult Cell disruption for further details.

Filtration

This step may not be necessary depending on the source of the cells. Animal tissue however is likely to yield connective tissue which must be removed. Commonly, filtration is achieved either by pouring through gauze or with a suction filter and the relevant grade ceramic filter.

Purification

Invariably achieved by Differential centrifugation - the sequential increase in gravitational force resulting in the sequential separation of organelles according to their density.

See also

• Cell disruption
• Differential centrifugation