DNA Quantification Problems

Thu Nov 18 16:58:16 EST 1999


Absorbance at 230nm can be due to polysaacharide contamination.
You can precipitate the polysaacharide contaminants by adding
1/10 vol of 3M Sodium Acetate pH 7.0 alone and removing
it by centrifugation (If your contamination is predominant
you should see a precipitate forming immediately after 
addition of Sodium Acetate). Afetr this, Ethanol precipitate
the DNA from the sup. 

Hope this helps

Suresh Kumar K.G.
skg at biochem.iisc.ernet.in

On Thu, 18 Nov 1999, Murat Eravci wrote:

> Hi!
> I make DNA Extractions from rat brain tissue using a genomic DNA isolation
> kit ("Wizard") from the company Promega. However, the spectrophotometric
> measurements of the 260nm and the 280nm seem to be OK but the value of 230nm
> (salts?) is much higher than the OD 260, so that I fear that the Value for
> the OD 260 is not correct. I have tied some procedures to wash the salts
> away (washing the DNA Pellet, after DNA precipitation with isopropanol, with
> 70% ethanol, but without success. Now I am thinking about filtration or
> dialysis.
> Could somebody help me to get rid of the Salts (or whatever the OD 230
> contamination could be) to decrease the OD at 230nm, so that I can measure
> correct DNA values at 260nm ?
> Thank You in advance!
> ~Murat

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