Homogeneity, ultracentrifugal

Microsomes Vesicles obtained from homogenized tissues by ultracentrifugation. They are derived mainly from the endoplasmic reticulum in the case of the liver (hepatic microsomes). 

A 0.5-2-kg crop sample is cut into small pieces and homogenized thoroughly using a food processor. Rice grain is milled with an ultracentrifuge mill and sieved through a 42-mesh screen. The typical size of an analytical sample is less than 50 g. To prevent the decomposition of the anilide residues, crop samples should be frozen soon after collection and maintained frozen until analyzed. 

Cereal samples are milled with an ultracentrifuge mill and sieved through a 42-mesh screen, then 20 g of the homogenized sample are transferred into a 300-mL Erlenmeyer flask and soaked in 40 mL of distilled water for 60 min. After 100 mL of acetone have been added to this flask, the same procedure as described in the case of vegetables is carried out. 

Ultracentrifugal mill Homogenizer Polytron mixer Mechanical shaker... 

Most organelle membranes, such as the tonoplast (6) and the Golgi apparatus (7), can be separated by density gradient ultracentrifugation of plant cell homogenates. However, other effective methods for the isolation of the plasma membrane (8,9) have been described. Moreover, another method that uses an aqueous two-phase system for the isolation of ER is also described (10). Those interested in these details for these methods should consult the original articles. 

Transfer the homogenate into precooled centrifuge bottles and centrifuge for 10 min at 2,400 x, 4°C. Collect the supernatant and discard the pellet. Transfer the supernatant to a precooled ultracentrifuge bottle and ultracentrifuge for 90 min at 34,000 x, 4°C. Discard the supernatant and resuspend the... 

For example, if the purpose of the experiment is to study the speciation of an element in a specific cell type in a given tissue it is essential that all the extracellular fluid is removed from the tissue before the homogenisation step. This step could be followed by ultracentrifugation of the homogenate in order to separate the cell under study from others that may be present in the medium. An estimate of the degree of purity of the end product should be given. The harvested cells may then be further processed. 

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