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Precipitating nucleic acids using either isopropanol or ethanol is a very common operation, and I've read some very different protocols on the duration and temperature the precipitation should be performed.

I've seen anything from precipitating at room-temperature and centrifugating immediately without any delay to precipitating at -20 °C over night in various protocols.

Is there any published data about the influence of duration and temperature on the yield of the nucleic acid precipitation?

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I think the folklore is influenced by how much nucleic acid you are working with. As @Daniel Standage suggests, some conditions wouldn't be influenced by anything. – bobthejoe Mar 29 '12 at 17:34
up vote 6 down vote accepted

I always did mine at -80 C, but I never compared the results to other protocols (I don't fix what's not broken). But, I was curious about the same thing, so I looked around. I found one paper discussing this: Paithankar and Prasad, Nuc Acids Res 19(6):1346 (1991)

It shows that at low concentrations, EtOH at RT actually outperforms the precipitations at both 4 C and dry ice/ethanol bath. That difference is quite big at 100ng/ml DNA and lost when there is more than 10 ug/ml DNA. For typical extractions, based on this data, I'd do it at RT.

On the other hand, Hilario and Mackay say in their book that:

for genomic DNA isolation, different DNA precipitation temperatures and incubation times have little effect on recovery rates. One can directly centrifuge after adding ethanol without the -20 C incubation, and, it -20 C ethanol is not available, room temperature ethanol can be used.

They do not, however, provide any citation for that statement.

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As a first year molecular biology student, I did a class project on this very question: trying to see if buffer temperature had an effect on yield during DNA precipitation. This is a far cry from peer reviewed research, but my finding was that there was no significant effect for a wide range of temperatures.

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