several bands in non-reducing SDS-page gel - protein without cysteines - (Oct/13/2014 )

Hi everybody,

I have a protein which does NOT have any cysteine. I know that it does form oligomeric structures and I hypothesised the complexes formed through non covalent bonds.

If I boil the sampIe and add a reducing agent into the loading buffer I get just one band (monomeric form).

If I run a non-reducing SDS-page gel using a sample loading buffer without beta-mercaptoethanol, I get several bands (corresponding to dimers and trimers sizes).

I knew that the difference between the two type of gels was that in the non-reducing gel the disulfide bonds are not destroyed so, if there are oligomeric structures, you can detect them.

But I don't have any cysteine and I thought boiling can destroy non-covalent bonds.

So, I did expect not to see any difference.

The question is: why I did get several bands in my non reducing gel even after boiling the samples at 95 C for 5 min?

Does anyone has any experience in this field and is willing to help?

I would really appreciate cause it's the first time I'm trying to address a similar question and I'm kind of lost.

Thank you in advance

you could be seeing aggregation caused by incubation at 95C. you can check for this by:

1) reducing the incubation time

2) reducing the incubation temperature (60-70C for 10-20 minutes)

3) omitting the incubation (you don't need the added energy to break sulfhydryl bonds)

Thank you!

This is very helpful :-)