Tris is highly soluble in water and is useful in the pH range 7.0-9.0. It is used in the preparation of Laemmli buffer, one of the most common SDS-PAGE buffers. In addition, Tris can also be used for many custom running and loading buffers, most often with glycine and SDS.

Application

Tris-HCl is just Tris base with an equivalent of HCl present for each molecule of Tris. So, it's essentially a version of Tris that has had its pH adjusted downwards before it even hits solution.