I have a question about the role of NaCl in the DNA extraction process. So for N

Question

I have a question about the role of NaCl in the DNA extraction process. So for NaCl concentrations under 0.5M, CTAB and DNA molecules can create complexes. In those concentrations, proteins and other hydrocarbons are still soluble in water except the DNA-CTAB complex. If we raise the concentration of NaCl then the complex of CTAB-DNA will be soluble to water too. Correct me if I'm wrong until now.

So I don't understand something. Why do we use NaCl?

Let's assume that we don't add NaCl. Will the CTAB create complex with DNA or not? As I read CTAB creates ionic bonds with DNA (phosphate groups). So in this situation (without NaCl) CTAB must be able to create complex with DNA too.

So why did we use NaCl? Just to keep proteins and other hydrocarbons soluble in the water or there is something else that NaCl helps in this complex creation?

Explanation / Answer

The CTAB-DNA complex precipitates when NaCl concentrations are between 0.5-0.7M at temperatures below 50 degrees centigrade. Since we dont want the precipitation but we want the pellet to retain its nature we have a salt concentration of 1M or above.

The CTAB-DNA complex is separated from the above solution and subjected to ethanol. CTAB is removed from the complex by the addition of ethanol and DNA is separately precipitated.

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