Re-use of magnetic beads in Promega's PolyA selection system

[Lely Chow]

Hi Everyone!

Would someone like to comment on the re-use of the streptavidin-coated 
magnetic beads for polyA selection?  I did this by mistake, and I found 
out that I now risk 1) reduced yield of polyA product; and 2)  
contamination of my mRNA with previous mRNA.  It seems as though my 
yields were not detectably reduced, which makes sense since I did not 
saturate the capacity 
of the beads the first time.  It is also possible that what little RNA was 
left over from a previous selection may not contribute greatly to the new 
batch of RNA, or that it has degraded with time (25 days at 4 oC).  I 
add approx. 60 ug of RNA to each tube (max.that can be added is 1 mg), and I 
reused 
each tube twice.  I am using the RNA on polyA dot blots to compare three 
treatment conditions.  

It would be nice to know whether I need to worry about contamination, since 
it is very difficult for me to 
get the RNA I need for these experiments, and I would like to avoid 
having to redo the experiments.

Hope someone has some helpful comments on this matter.  Thanks for your time.

--Lely Chow