As we know when we treat a protein with SDS, it breaks non covalent bonds to form primary structure. But how it adds negative charges uniformly on all constituent amino acids?
The SDS–protein complexes all contain about the same negative charge because the SDS swamps out all of the protein charges. Since the charges are all the same, the proteins all separate from one another strictly on the basis of their sizes.
Dear Ahmad
the SDS is an anionic detergent with negative charge and its binding to the proteins oats the protein with a uniform negative charge, which masks the intrinsic charges on the R-group.
There is also a special king of native page named blue native page where the SDS is replaced by comassie blue which is not able to denature the protein but it still able to confer to them an weak and uniform negative charge which allow to them to be solved on the basis of their MW and not the MW/charge ratio as happen in the standard native page.
If you are interested on my blog ProteoCool is avaialble a video named Overwiev on SDS-page where you can find other informations
https://www.blogger.com/video.g?token=AD6v5dyp2LLPNQObE-O7xpUxV02oGcx4RQ0mfxIRjK1x1YHBCYw3Av9JZTXdeO6JXLu6wl6Cd2omOIASqXY7BDpDcvlzrJ8fQSoqXnMyd5Fqcc3vRe-1JCCyISDv7Y-UACmOPKhEV6M
ciao
Manuele