DNA precipitation - A general question about DNA precipitation (Jul/19/2011 )

Hello!

Just a simple question. I want to precipitate a band of around 300 bp of DNA using sodium acetate + EtOH.
I have done this a hundred of times without problems, but I always ask myself the following question:

Do you think a small DNA fragment will precipitate better at -80 ºC for 20 minutes, or at least 2 hours at -20 ºC?
What do you usually do?

Thank you in advance!

I think 2 hours at -20 degree is better. I think it is kindda like u give more time but a higher temp for a saturated solution to form an ordered crystal.

We normally just do 20 minutes on ice followed by spinning.. Is the longer time helpful just for the smaller fragments?

I always no matter the the size of DNA use cold alcohol (ETOH absolute for small fragment DNA and 2-propanol for large I keep them at -20C) and let the precipitation for overnight at -20C it takes time I know but after several years thats what works for me, specially when working with samples that have a low yield.