What you describe is the preparation of electrode buffer, not sample buffer, for Lämmli SDS-PAGE gels. The glycine is essential to create the sharp boundary between the electrode buffer and the stacking gel buffer, which is required to focus the proteins in the sample in a sharp band befoe the enter the separating gel.

Pierre Béguin oh, I said about loading buffer when Lämmli SDS-PAGE, when fill loading gel and stacking gel during electrophoresis. That buffer set pH by tris and glycine, if pH is too high or too low, add tris or glycine neither use hydrochloric acid nor sodium hydroxide.

then when use HCl or NaOH, glycins cannot its role?

Hi there,

Tris-HCl buffer system is used for stacking and separating gels (with ifferent pHs) as well as for loading buffer preparation whereas Tris-Glycine system is used only for the running buffer preparation. In this latter case Glycine is the proton donor to protonate the Tris Base for pH adjustment (just like HCl is in the Tris-HCl system).