2HPO4, 20 mM KH2PO4, 27 mM KCl, and 1.37 M NaCl, and 1% Tween-20. pH 7.4 .2. Prepared in 3D water and autoclaved at 15 psi for 20 min on liquid cycle. The pH of the 1X should be pH 7.4 .2. To make 1X, dilute 10-fold with 3D water. Shipped at room temperature, store at room temperature.