Fixing sequencing gels

Kilroy, Gail - Dr. York 2545 kilroyge%pbrc at
Tue Aug 2 15:41:45 EST 1994

>010Date: 29-Jul-94 11:27:33 -0600
>From: HORTON @ XGATE (Robert Horton) {horton at}
>To: METHODS- @ XGATE {methods-and-reagents at}
>001Subject: Re: Fixing sequencing gels
>  To: methods-and-reagents at
>  From: horton at (Robert Horton)
>Chris Greene (cgreene at wrote:
>: In article 1125646336B at, cupton at ( Chris Upton) writes:
>: > In response to an article in Biotechniques (FEB '94, Yang & Waldman), that
>: > suggested it wasn't necessary to fix 35S seq gels but that the Saran Wrap
>: > should be left on - I persuaded a grad student next door to try this :-)
>: > 
>: > He found it worked fine!! (to think of all the time I spent fixing gels!!)
>: > 
>: > BUT, he also took off the Saran Wrap!!  & there was _NO_ problem with the
>: > gel sticking to the film!!
>: > 
>: > This may be because he dried the gels very well or low local humidity.
>: > I guess it's something to test yourself.
>: > 
>  <snip> 
>: I have been exposing my sequencing films in this way for about two
>: years now, and it does indeed work fine.  One thing you must be careful
>: of is that the gel must be dry if you remove the plastic film.  I'm
>: sure that when the humidity levels rise once again you will finds lots
>: of little black dots all over your film where the gel stuck.  This
>: tends to make the film rather unsightly but can still be read quite
>: easily.
>  <snip>
>I do it this way, and rarely have problems - you need to be quite sure the
>gel is dry, though. This is in Minnesota, where the humidity is not usually
>severe. Our gels are lifted onto 3MM paper, and dried at 80oC for about 60
>-90 minutes, using a water aspirator. On a humid day, it may be important
>to expose the gel to film right away, so it doesn't sit around rehydrating.
>But I think the vast majority of the urea is sucked into or through the paper
>anyway, so rehydration is not as much of a problem as one might think.
>It would be interesting to hear from people in REALLY humid places about
>how this works (anybody NOT fix their gels in Baltimore?)
>The idea that different techniques work in different places is intriguing;
>I knew a guy who was a sequencing wizard in Minnesota, but he went off to do
>a postdoc in France, and (after much frustration) he had to adopt a different
>set of procedures, particularly with regard to preparing the plates.
>Something in the water, he thought.
>Anyway, ... if it ain't broke, don't fix it. (Somebody had to say that B^)  ).
>Bob Horton (Ph.D.!)   /\ "Crash programs fail because of the theory that
>U. of Minnesota, CBS  || with nine women pregnant you get a baby a month" 
>1479 Gortner Ave.    /||\   -Werner von Braun.  Disclaimer:"Bob who?"
>St. Paul, MN 55108    ^^   horton at 624-3790

I've been drying my sequencing gels without fixing for several years and
even in Louisiana, where the humidity lingers around 95%, there isn't a
problem.  What I've done, when leaving the saran wrap on would present a
problem, is spray a thin coat of silicone over the gel. You can pick up an
aresol can of silicone at your local hardware store.  The silicone does not
seem to block the signal.

More information about the Methods mailing list