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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?

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2 Answers 2

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CTAB forms insoluble complexes with nucleic acids and can be used to selectively precipitate them from solutions, see this reference:

When you add NaCl in a concentration between 0.4 - 0.7M, the nucleic acids stay in solution, while polysaccerides and other substances, which may interfere with the DNA preparation do not. See this paper: "Rapid isolation of high molecular weight plant DNA."

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DNA negatively charged so it repel. It won't come together for pelleting. so Na+ ion from NaCl binds with the negatively charged DNA and Neutralize. Thus Na+ prevents the repelling of DNA & DNA molecules come together as fibers during the procedure.

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Can you please rephrase your answer? I Ihink I know what you are trying to say, but at the moment this is hard to understand. –  Chris Sep 10 at 18:17

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