I know that nucleic acids (both RNA and DNA) precipitate out in 100% ethanol.
What is the reason why RNA binds to the silica membrane in the pink spin column, with little DNA binding-is it because Qiagen have a proprietry (i.e. secret) type of membrane that only binds RNA and little DNA or is it because of the chemicals in the extraction buffers (RLT AND RL (both a secret as well) allow only RNA to bind?
Hi please see a very similar discussion at https://www.researchgate.net/post/How_do_silica_based_RNA_spin_columns_only_bind_RNA_and_not_DNA
Thank you
I have read this researchgate discussion previously . It gives no reliable , logical information.
I kept digging and eventually found 2007 US patent 7,208,271 file:///C:/Users/PETERN~1/AppData/Local/Temp/US7208271.pdf
-To selectively bind DNA to silica requires a extraction/lysis buffer with alkaline Ph and a salt with a large anion equal or bigger than a bromide ion.
-To selectively bind RNA to silica requires a extraction/lysis buffer with a neutral or acidic Ph (acidic preferable) and a salt with an anion smaller than the bromide ion.
The 'secret' buffers from qiagen contain the above chemistry.
There is not secret in the principle. Both RNA and DNA bind to silica and you get both in extraction. Most of the kits has some sort of DNAase digestion step which removes the DNA contamination from RNA sample.
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