Do proteins break up on SDS PAGE treatment?

Ian A. York iayork at
Fri Nov 17 12:29:44 EST 2000

In article <8v3lrs$7j6$1 at>,
Student <mucineer at> wrote:
>Do proteins break up by heating with SDS buffer at 70 degrees for 10
>minutes? I found that when I ran a non-reduced SDS PAGE gel on a purified
>protein (IgG purified from a protein column), although the vast majority of
>the product is at the right size, there are some faint bands scattered
>below. I am quite sure that they are not contaminants because when I ran a
>reduced gel, they weren't there (just one very faint band as opposed to 4 or
>5 in the non-reduced gel), yet they both came from the same sample!

If you did not see the bands in the reduced gel, but did see them in the
non-reduced, it seems unlikely that it's a question of degradation or
cleavage; the reducing gel should show that more clearly, not less.

Possibly your protein has internal disulphide bonds (perhaps only in a
small fraction of the total; perhaps artifactually introduced, or
misfolded during synthesis); if so, the non-reducing gel will allow these
proteins to remain in their more compact form (folded, rather than
completely linearized) and so they'll run faster than the completely
linear molecule.

    Ian York   (iayork at  <>
    "-but as he was a York, I am rather inclined to suppose him a
     very respectable Man." -Jane Austen, The History of England

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