1.6.1. Buffers

1. prepare 100 ml of a 0.02M phosphate-buffered saline (PBS) from the following stock solutions:

   1.1.  1.9 ml of 0.2 M NaH2PO4xH2O,
   1.2.  8.1 ml of 0.2 M Na2HPO4xH2O,
   1.3.  0.9 g NaCl,
   1.4.  80 ml ddH2O,
   1.5. Adjust pH to 7.4,
   1.6.  Complete volume to  100 ml.

2. Prepare a microtubule Stabilization Buffer containing:

   2.1.  HEPES buffer (25 mM, pH 6.8),
   2.2.  25 % glycerol,
   2.3.  0.5 mM MgCl2,
   2.4.  25 µM phenylmethyl sulfonyl fluoride (PMSF),
   2.5.  1 % Triton X-100,
   2.6.  0.01 % sodium azide.

All molarities and % given as final concentrations. 

HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) is a zwitterionic organic chemical buffering agent. It is widely used in cell culture media for maintaining a physiological pH level. PMSF is a serine protease inhibitor which is best prepared as a stock solution of 25mM PMSF in ethanol. Triton X-100 is a detergent, so it should be added to the buffer only after adjusting the pH. Sodium azide is a common preservative of samples and stock solutions, acting as a bacteriostatic.