Complete removal of DNA

The amount of SAN and time needed for complete removal of DNA will depend on the extract.

A typical cell lysate contains DNA, RNA, nucleotide-binding proteins, lipids, detergents etc. and is more complex than an optimal DNA-containing reaction buffer. Thus, for complete removal of DNA in a bacterial lysate more SAN is commonly needed than for buffered solutions.

To enhance dissociation of DNA from proteins, making DNA available for degradation, adjust the concentration of NaCl to 0.5 M and incubate at 4°C overnight. Then add SAN and incubate at 25°C for 30 minutes. The amount of SAN needed will depend on the extract composition as well as incubation time and temperature, but is commonly between 50-1000 U/ml. The removal of DNA from the extract should be verified using agarose gel electrophoresis.

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Complete removal of DNA

Figure 1: Addition of salt leads to DNA dissociation from proteins, making it available for degradation by the highly active SAN.