ETBr in Loading Buffer

Moshi Kotierk mkotierk at
Tue Feb 5 19:14:35 EST 2002

D Picton (pictond at wrote:
> I was wondering if anyone has ever tried or knows why Ethidium Bromide
> is not added to Loading buffer? I've never run across an article where
> Ethidium Bromide is present in the Loading Buffer, it's allways
> present either in the gel or as a post electorphoresis step.

I was under the impression that EtBr is positively charged, whereas DNA is
negatively charged.  As such, if you load it onto the gel in the loading
buffer, the EtBr and DNA should go separate ways.  If you look at a gel
that contains EtBr on a transilluminator after you have run it for a
while, you should see (at least, I usually do)  a band at the bottom that is
less fluorescent. 

Moshi Kotierk
Carleton University

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