Buffer that is useful in the pH 6.3-9.5 range. This wide buffering range is due to its two pKa values, 6.8 (pKa1) and 9.0 (pKa2), being so close. Because of the wide buffering range, particularly down to pH 6 - 7, this buffer has been used to enhance the stability or activity of restriction enzymes, compared to Tris buffer (which is a poor buffer below pH 7.5 and has a comparatively large change in pKa with temperature).