Recommended concentrations for use are approximate values. A dose dependent response assay should be performed to determine the optimal concentration for use in specific applications. Dilute tat stock solution in saline-phosphate buffer (150mM NaCl, 50mM sodiumphosphate, pH 6.5) immediately before use. Tat readily oxidizes in buffer solutions which may change its LTR- dependent transcriptional activation activity.Transcriptional activation assays with tat are performed in 1-10�g/ml range. ELISA and Western ELISA require tat in 10-100ng protein range.