Protein dimers on SDS gels -- Can they be non-covalent?

mcmahan at mcmahan at
Tue Sep 20 01:37:37 EST 1994

I recently purified a an overexpressed protein from E. coli.  When I ran the
sample over a anion exchange column, I got two peaks with very similar elution
times.  When I examine these two on SDS-PAGE/Western blot, the first peak was
the right size.  The second peak was mostly the right size with an additional
band that also cross reacted with the monoclonal.  It size is roughly that of
a dimer.  The dimerization is resistant to 0.1 M DTT so is probably not a
disulphide.  Does anyone know of other associations that could be going on?
Is it possible that a non-covalent association could be resistant to SDS?
Could some other reaction be occuring other disulphide formation i.e.
dehydrolysis of a COOH and a OH to form the ester.  I should add that the
protein forms inclusion bodies in the cell and it is from these that the
protein is purified.  Any references anyone has on this topic would be much
appreciated.  email me at mcmahan at  Thank you

                                                 Scott McMahan

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