The most widely used subcellular fractionation techniques (e.g., centrifugation) are dependent on differences in physical parameters between organelles (e.g., size and density). In contrast, immunological techniques rely on biological differences, i.e., the expression of different antigens. The most popular immunological method for subcellular fractionation is immunoadsorption onto a solid phase, which offers the prospect of fast purification in high yield under conditions that do not expose organelles to unusual media or to osmotic shock. Immunoisolation techniques also have the advantage of being applicable to situations where only a small amount of cell material is available, e.g., tissue culture cells.
