RNase A in Qiagen buffer P1

S. Schoenfeld "sschoe2 [remove.this.spam.tag]" at uic.edu
Thu Dec 23 13:33:50 EST 2004

Hi all I have a question about RNase A and column vs non column minpreps.

In Qiagen RNase A is added to the initial resuspension buffer.  I am unsure 
as to what good this does as in P1 the RNA/DNA is still in the bacterial 
cells.  When the alkaline lysis buffer is added in P2 the DNA/RNA is 
released but I read RNase A is inactivated in .1% SDS (P2 is 1% SDS).  In 
any case RNA generally does not bind to the silica columns that much anyways 
so the columns remove the RNA.

I have been using the Qiagen buffer to do the alkaline lysis then doing 
phenol/chloroform extraction followed by ethanol precip.  When I do this  at 
the end there is a bright RNA band on the gel around 50-100bp.  Qiagen 
claims in their manual this is RNase A-resistant RNA.

My question is will precipitating the DNA/RNA after the lysis and 
resuspending in TE/RNase then doing PC extraction and another alcohol 
precipitation remove the RNA because RNase A is inactivated in SDS or is 
Qiagen correct in saying this RNA is simply resistant? 

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