Write up on mechanism of DNA precipitation?

Answer 1

DNA molecules are surrounded by water molecules when they are in solution. This is called the shell of hydration.

When the salt concentration of the solution is increased, the sale molecules replace the water molecules in the shell of hydration causing the DNA to come out of solution. This 'coming out' of the DNA from a soluble form is called DNA precipitation.

Precipitated DNA generally is surrounded by a lot of salt and has to therefore be placed in a low salt buffer in order to make sure it remains pure and integral (in an unbroken state)

Answer 2

DNA precipitation involves the addition of a salt (such as sodium acetate) and alcohol (like ethanol) to a DNA solution, which disrupts the hydrogen bonds between DNA strands and water molecules, causing the DNA to aggregate and form a visible precipitate. The negatively charged phosphate groups on the DNA backbone are neutralized by the positively charged ions in the salt, reducing its solubility in water. The addition of alcohol promotes the precipitation by further reducing DNA solubility and causing dehydration of the DNA molecules, leading to their aggregation and precipitation.