How low can you go (Nuc Acid pellets)?

[Marion Freistadt]

This is not exactly what is being asked, but I learned in graduate school
that a general rule is that DNA at less than 10 ug/ml does not recoverably
precipitate, but above that does.  In my experience, even pellets with a
fair amount of DNA are invisible, especially if they are very clean.  You
can try adding glycogen, which, in addition to being a good carrier makes a
distinctive glossy pellet.


>In article <1994Mar21.223751.28764 at emba.uvm.edu> Brian Foley,
>brianf at med.uvm.edu writes:
>>David Sang-shin Lee (davidlee at whitman.ccs.itd.umich.edu) wrote:
>>: I was wondering....When precipitating DNA or RNA, how little nucleic
>acid
>>: can you have before the pellet (after centrifugation) becomes so small
>>: it's invisible?
>>
>>      It depends on how good your eyesight is, and how clean your DNA
>>is.  Often times the pellet I see is mostly "other stuff" and not DNA.
>I
>>know that when I use real pure DNA for sequencing I cannot see the
>pellet
>>when I have precipitated 5 micrograms of plasmid.
>
>It also depends on the size and conformation of the DNA.  Long, linear
>DNA precipitates are more easily seen than closed, circular, coiled
>plasmid DNA which is more easily seen than the same amount of small PCR
>fragment which is more easily seen than oligonucletide precipitates.
>
>I do not have any numbers off the top of my head, but that has been my
>experience.
>
>Good luck,
>
>Jim Owens
>
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