black dots on western blots

Michael Witty mw132 at
Wed Mar 14 03:57:23 EST 2001

> Here is what I concluded about dots problem for myself:
> Dots are result of small pieces of gel sticking to the
> membrane. Antibody can get trapped in the gel, and then are
> washed out poorly (diffusional problems), resulting in 
> intense localized signal upon development with low MW 
> substrates. That's why most of the dots are usually 
> located on the periphery of the blot - where gels 
> tend to stick most. 
> Now I inspect blots visually and try to remove any 
> gel pieces with a jet from squeeze bottle. I think
> it helps.
>         - Dima

In my case it was bubbles sticking persistantly to the membrane.  I had to
use a gloved finder to poke and squash them off the membrane during
blotting and washing.  Mike.

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