3.5.1.38 2-mercaptoethanol slight activation 209094 3.5.1.38 cysteine slight activation 209094 3.5.1.38 dithiothreitol slight activation 209094 3.5.1.38 additional information use of phosphate buffer yields higher activities than Tris, phthalate, or citrate buffer, optimum concentration is 0.08 - 0.16 M phosphate 687356