I need a stable DNA solution at 37℃. I have some herring sperm DNA, but there solution about 20ug/ml in HEPES (pH 7.4, 10mM) is unstable at 37℃. The UV absorption decreased after 2 days at 37 ℃. I believe some DNA precipitated from the solution.
so, is there any DNA that can be stable in any buffer (pH about 7) at 37 ℃ ?
thanks.
I don't think the problem is with the stability of the DNA. It should be stable at 37oC at neutral pH, as in nature. If the UV absorbance decreased, it may be because some of the DNA was adsorbed onto surfaces. You had a pretty low DNA concentration, so just a little surface adsorption would be noticeable.
If you had seen a UV absorbance increase, I would have suggested that the DNA was degraded by DNase.
DNA is very stable .How are you measuring the dna, I think that a proper blank for zeroing the spectrometer would be the buffer that had also been incubated at37 for 2 days and did the HEPES have any dye indicator that might have a UV absorbance but probably Adam is right and anso[tion is an issue. If it is so then adding more dna might be stable as the glass surface will be saturated with dna mplecules so it might be worth adding some more or pre soaking the container and testing again
Totally agree with the above two answers. I explain this to students this way: think of all the different conditions DNA has to be stable in to support life. This doesn't change when you have it in a buffered solution on the bench, in the fridge, in the waterbath, etc.
If you are worried that it is degrading in some way, you can always run it on a gel to check for fragmentation. This is a very quick and easy way to check.
I agree that DNA will bind to plastic surfaces and might explain your finding (although I'm not sure the amounts that you can accurately determine by UV are in the range that would be detectable). However, I'm sorry to contradict, but DNA is not stable in neutral aqueous solution at 37oC: it loses purine and pyrimidine bases by hydrolysis at a rate that was described some years ago by Tomas Lindahl and others.
That might not be a significant instability for your experiments, but you haven't told us what your criterion for stability is.
I agree with the rest fo comments, except for that of Geoff regarding the stability of DNA at 37ºC; if the buffer is TE, it should be stable at 37ºC; if it was dissolved in water, then geoff is correct
And yes, DNA can precipitate and adsorb to plastic surface. Try heating it to eg 60ºC and gently shaking the solution to redisolve it
Iker, I politely refer you to: https://www.ncbi.nlm.nih.gov/pubmed/8469282
and references therein.
Also, Wenchao will want to know where you got your information about DNA stability in buffer versus water (me too).
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