TROPLIST: Morpholino losing activity in solution over time

[Jon D.Moulton]

Hi folks, it's Jon from Gene Tools.

We've learned that Morpholinos can associate with the inside walls of 
their containers, decreasing the solution concentration.  Many oligos 
don't do this, but it has occurred often enough that we now suggest 
keeping your Morpholino solutions at room temperature.  People whose 
labs have switched from cold storage to room temperature storage haven't 
been reporting any more problems with loss of activity.  If you have an 
oligo that has lost activity and the heating protocol Ira wrote about 
isn't bringing the activity back, try autoclaving the solution (with the 
vacuum dry cycle disabled).  Morpholinos can take the heat, though I 
wouldn't do it routinely, and the solvent collisions might be energetic 
enough to knock the oligos off the walls.

For storage, I would wrap the vial closure in Parafilm (to help keep 
microbes out) and put the oligos in a dark box (to avoid photobleaching 
fluorochromes) on a lab shelf.  They should be fine for years that way.

Best wishes,

  - Jon
jmoulton@gene-tools.com

Dear Troplisters,

I would like to ask you if you have found that some of your morpholino
oligos might have lost their "activity" over time?  I have just determined
that a morpholino I have been keeping at -20oC for the past 5 years and
now have a reason to dig out for an experiment, no longer has the youthful
vigor it once did.  I am aware that many people heat their morpholinos to
65oC for a short time before injecting, to improve solubility, etc.  This
also failed to divert my embryos from their normal development.  So I
thought I'd send out this email to see what others in the community have
experienced.  Thanks for any comments you might have.

Sincerely,

Ira