(no subject)

[Helen Haase]

I've been successfully doing Northerns for some time looking at mRNAs 
which range in size from 1-12kb.  The largest mRNA (12kb) has the lowest 
expression level.  Recently I lost the ability to detect this message.  
Using newly prepared probe (both cDNA and riboprobe) did not change the 
situation.  I now suspect that the transfer procedure from gel to 
membrane is to blame.  However I have not altered my protocol, which is 
to do a capillary blot O/N from 10XSSC to a positively charged nylon 
membrane (Boehringer Membrane).  All other targets I look for are 
present in expected quantities.  Has anyone else experienced problems 
with transfer of higher molecular weight RNA?  If so what are your 
suggestions?

Science is such fun!!
Helen