Beta-mercaptoethanol in SDS-PAGE

Beta-mercaptoethanol is a reducing agent in the loading buffer that cleaves disulfide bonds, which are unaffected by SDS. Together with SDS, it ensures the unfolding of the protein, making the structure of the protein primary. The primary structure is necessary for the separation of proteins to be based on their molecular weight rather than their shape.

Illustration of a protein before and after the influence of beta-mercaptoethanol. To the left is an unaffected protein in its regular structure that is held together in a folded formation by hydrogen, ionic and disulphide bonds together with hydrophobic interactions. To the right is the influenced protein in a slightly unfolded structure where all disulphide bonds have been cleaved.

Figure 1. Effect of beta-mercaptoethanol on a protein: Protein before and after the effect of beta-mercaptoethanol.