DNA/RNA ethanol precipitation

VALLAN at ubeclu.unibe.ch VALLAN at ubeclu.unibe.ch
Thu Jun 1 03:53:49 EST 1995

I have some quite basic questions concerning the centrifugation times
for DNA and RNA precipitation with ethanol.

Looking at different protocols I found suggestions for centrifugation
times which range from 5 to 30 minutes in a microcentrifuge at full speed.
Since loing I wonder what the optimal time really is. Is there more DNA
recovery if one centrifugues 30 instead of 10 minutes? Is this dependend
on the length and concentration of the DNA in the tube or on the volume
of the DNA solution? What is the optimal centrifugation time for the
washing step? ( I found times from 2 to 15 minutes) And finally what is 
the optimal incubation time at -70 degrees before centrifugation? Or is
an incubation at -20 degrees enough?

While I'm at it: some people say that it is better if before putting
the DNA in the cold bath one mixes the solution without vortexing it.
Can somebody confirm this or is this just esoterics?

I would very much appreciate if somebody could give me a reference
where I could look up the answers to all these questions.

Thank you and sorry if the questions are too basic


E-Mail: Vallan at ubeclu.unibe.ch

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