Bio-Rad PureZOL™ RNA Isolation Reagent - Manual (Page 8)

Section 4
Recommendations for Best Results
• When isolating RNA from small sample sizes (<500,000 cells or
<10 mg of tissue), lyse or homogenize in 0.8 ml of PureZOL.
Use glycogen as an RNA carrier by adding 5 µl of a 20 mg/ml
glycogen solution (not provided) to the aqueous phase before
precipitation with isopropyl alcohol. Carry out precipitation for
30 minutes at 4°C.
• Frozen tissues should be kept at –70°C prior to homogenization
and thawed in the appropriate volume of PureZOL RNA isolation
reagent.
• An additional step may need to be performed for samples with
a high content of proteins, lipid, polysaccharides, or
extracellular material, such as muscles, fat tissue, and tuberous
parts of plants. Following homogenization, remove insoluble
material by centrifuging the homogenate at 12,000 x g for
10 minutes at 4°C. The resulting pellet contains the insoluble,
extracellular components, such as polysaccharides and high
molecular weight material, while the supernatant contains the
RNA. In samples from fat tissue, the excess layer of fat that
collects at the top should be removed. Transfer the cleared
homogenate to a new RNase-free tube and continue with the
RNA extraction protocol.
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