Hydrochloric acid in SDS-PAGE

Hydrochloric acid or HCl is added to the loading buffer, usually in the form of Tris-HCl, to help pull the proteins along the gel. The negative charge of the Cl ions means they move faster through the gel than the proteins. The Cl ions also work in conjunction with glycine in the running buffer to line up the samples in the stacking gel layer, so all samples enter the separating gel at the same time.