Tue Jul 9 16:10:02 EST 1991

>   Has anybody out there got a good method for visualising DNA fragments
>of less than 1kb in agarose gels? We routinely incorporate ethidium
>bromide into the gel before starting electrophoresis, and while this
>shows up the larger bands, resolution at the bottom of the gel is always
>lousy. What's the answer?? is it better to soak the gel in ethidium
>bromide after electrophoresis? Hope this isn't too daft a question.
>All the best

What size difference do you want to resolve?

We have "sharp" bands (they look pretty in photos) down to ca 300 bp in 
1% agarose, and down to 200 bp in 2%, with 0.5 microgram/ml ethidium, 
tris/phosphate buffer.  Don't let the gel run too warm, and photograph 
immediately when done.  My experience with gels soaked after running is that 
they're not as sharp, and more DNA is required for the same intensity of band.

Bill Melchior
National Center for Toxicological Research
Jefferson, AR  72079
(501) 543-7206

wmelchior at ntdoc.nctnet.gov

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