Is there is any easy protocol to redissolve the undissolved DNA pellet caused by over drying ?
It may be contaminated from protein which is less dissolve in TE. Do a phenol chloroform extraction and dissolve the new pellet of DNA.
Or other wise the amount of DNA in the pellet may high and TE may not enough to dissolve all the DNA in the pellet.
I have both lyophilized and ethanol precipitated a pellet of DNA to dryness. All it takes is 10-15 min in water solution to dissolve. If that is not working for you, then you probably didn't have DNA in your pellet to begin with.
I am not aware that there is such a thing as "overdried" DNA.
How was the pellet of DNA, if that is what it is, produced?
If you need your DNA to be doublestranded, do not dissolve in water, use a buffer such as TE.
If there has been DNA in the pellet, what was there might actually have dissolved: spin and check the supernatant by nanodrop or picogreen assay, or run an agarose gel stained with gel red.
It may be contaminated from protein which is less dissolve in TE. Do a phenol chloroform extraction and dissolve the new pellet of DNA.
Or other wise the amount of DNA in the pellet may high and TE may not enough to dissolve all the DNA in the pellet.
I agree with Margison. In 35 years of DNA extractions undissolved supposed DNA pellets were not DNA pellets. Finally, are you sure of your TE? Throw it out and prepare a freshly brewed one.
I agree with others (having work with all kind of cells from whixh I extracted DNA), DNA should dissolve quickly in TE, especially if you warm it at 37°C. If you still have a pellet, it is definitely not DNA.
After reading the "quick protocol", I have two options. Either you pipet back proteins at the step where you should have precipitated them, or you have RNA contamination.
I have had overdried pellets that would not dissolve no matter what I did - I must admit, however, that as I could never dissolve it I don't actually know if it was DNA or had some other contaminant. In any case, sometimes heating helped a little, but really the best answer is to just try again.
Jean-Yves: so do you think that RNA is less soluble than DNA?
Amanda: by now you should get the idea that if it will not dissolve, it is not DNA: the term "ovedried DNA" is both incorrect and misleading.
Geoff : By experience if the term of "overdried DNA" is incorrect, I would not be so affirmative about RNA. Not having to extract the RNA in any conditions, I would not be completely sure. However, I did get a white pellet (the DNA one is often brownish), I could not dissolve in DNA extractions cleaned of protein (controled).
Jean-Yves: my own experience is that RNA is more soluble, by that I mean dissolves more rapidly (in neutral pH, aqueous buffers), than DNA. I just wondered if you had a different view!
Brown DNA, again in my experience, isn't pure DNA: dry DNA is "as white as the driven snow"
When I have been sent such "DNA" pellets, I add 100uL TE (not water) and carefully sonicate (for me the size od the DNA is not important) then centrifuge and take off the supernatant. I quantify DNA by picogreen assay.
Others have suggested simply incubating for suitable times at 37oC and you have already mentioned that you used 65Celcius for 1 hour. That should have been OK for dissolving out the DNA, so did you check the supernatants??
I used a probe sonicator, but these vary so much from model to model its impossible to state what conditions you should use. If you have your "DNA" sample in a tube (Eppendorf perhaps) add to an empty tube whatever volume of TE you added to your DNA. Set the sonicator at low power and check that the TE is not blown out of the tube. Reduce power until that doesn't happen. If you have a thermocouple thermometer, check also the temperature increase in the TE test and keep that to 50-60Celcius at the most (for 100uL TE at 30% power on our sonicator, that might take about 20 seconds). then apply those conditions to your sample. If you have only a sonicator bath, this is much easier to control. Simply insert the tubes into a polystyrene tray and sonicate them for (I guess) 30 mins (with the correct water level in the tank!).
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