RNA with DNA contamination - (Sep/29/2004 )

I isolate RNA with a kit of RNA easy mini kit(GIAGEN). AFter homogenize, I put my samples into -70C refrigerator for a week. Later I continue to isolate RNA. I find OD260/OD280 of my RNA is rather low as below 1.6. Gel results further prove that it is contaminated by DNA. Can you tell me THE REASON?

DNA as well as RNA is bound by the matrix of the spin column. The companies try to match their buffer etc. in such a way that the binding of the unwanted nucelic-acids is minimised, but it's still there.

So what we do and what i would recommend to you is DNaseI digestion of your RNA. Either with the enzyme supplied by the company of the spin columns with an on column digest or with another enzyme from another supplier, doesn't matter much!

mike