TBE precipitation

Joan Marie Shields jshields at rigel.oac.uci.edu
Thu Aug 12 13:06:58 EST 1999

XL wrote:
>> I am running a lot of DNA sequencing gels in my lab. One of the reagents we
>> use routinely is the TBE. We usually make a 10X stock and make dilution from
>> there. As many of you may already notice that 10XTBE will precipitate after
>> the stock is used/opened.  I am trying to get some chemistry explanations
>> about this precipitation. Is it because of the solubility, pH or chemical
>> reactions with air?  Thank you.

Colin Rasmussen <colin at pombe.usask.ca> wrote:
>I think the borate has a tendency to ppt. with time.  We found in the
>past that autoclaving it helps for some reason.  Alternatively, make 5 x
>TBE.  That always solves the problem.  We typically run our gels in 0.5
>x TBE so you won't wind up making any more than you are now.

I was having trouble with it precipitating as well - autoclaving seems to 
have solved that problem.

I will say regarding the 0.5x - I typically run fairly high percentage 
agarose gels (2-4%) and I've found that if I use 0.5x TBE that my bands
aren't nearly as sharp.  I've gone back to using 1x TBE and have had much
better results.

Joan Shields       jshields at uci.edu       http://www.ags.uci.edu/~jshields
University of California - Irvine         School of Social Ecology
Department of Environmental Analysis and Design
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