RED RAIN: possible simple solution

Steven Steven
Wed Dec 4 17:17:45 EST 1996

G'day All

					There has been a lot of concern over the reason, course and 
solution for the infamous "RED RAIN" problem that has been appearing 
,in ABI-377 gels.  Following are my observations and possible simple 
solution to eliminate the course.  For those that do experience this 
"RED RAIN"  (and due to the course not everyone is going to be as 
likely to observe the problem) please try this simple solution and let 
me know, as well as others, whether this really is a solution.

				Reason: I guess most people will have observed by know the the 
reason for the "RED RAIN" is that bubbles get in front of the optics.  
You can observe these bubbles by looking at you gel once it has 
finished running (and you have "RED RAIN").  Remove the heater plate 
and lift up the cross bar in front of the optics.  These bubbles have 
migrated (floated) from the bottom of the gel up.  These bubbles are 
between the gel and the glass plate as opposed to bubbles in the gel 
itself.  You can induce getting these bubbles i.e. make "RED RAIN" 
(you can do this on a freshly used gel) by just lightly sticking a 
spatula in at the bottom of your plate, jiggle it around, creating 
bubbles in the plate then put it back in the ABI-377 and do plate 

				Course:  The course for the above problem, i.e. the reason the 
bubbles get there is due to drying of the gel as the gel is 
polymerising.   This courses the gel to wrinkle at the bottom.   For 
the polymerisation to give a good gel it has to have the correct media 
(water) volume and stability (no evaporation) to work.  As the gel is 
polymerising and drying these wrinkles appear where bubbles can be 
introduced and then these bubbles migrate up through these wrinkles.  
I had gotten to the point where I had 100% success rate for predicting 
which gels would produce "RED RAIN" (out of 15 gels run).

				Solution:  I have found that by putting a wet paper towel on the 
bottom of the gel once it is poured, either on the Otter or as I do it 
by tapping the solution down.  This will keep the humidity up for the 
gel and therefore will not have evaporation.  Observing the gel that 
is made this way you should observe that there is no wrinkling of the 
gel at the bottom, and even after the gel has been run the bottom will 
still be nice and even.

				Well I hope this may help clear up some problems for all out 
there.  I am still using the wet towel method and haven't seen "RED 
RAIN."  Hopefully this was a simple solution and not just that it 
happened to be good gels (hard to have good controls to totally test 
this other than statistics and observation).  Let us all know what you 
all think.


Stephen Toth
Genome Therapeutics Corp.
100 Beaver St.
Waltham, MA  02154
tel:  617-893-5007 X2551
				617-398-2551 (direct line)
fax:  617-893-9535
      617-642-0310 (back-up)
toth at cric.com

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