How low can you go (Nuc Acid pellets)?

Jim Owens jow at helix.nih.gov
Fri Mar 25 08:43:31 EST 1994


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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