Then, a 50-lL volume of 0.1 mM oleate ester of fluorescent 4- methylumbelliferone (4-MUO) solution (0.1 mM) and 20 lL of
13 mM Tris–HCl buffer containing 150 mM NaCl, and 1.3 mM CaCl2, pH = 8.0, were added to the solution. After incubation at
room temperature for 30 min, 100 lL of 0.1 M sodium citrate (pH = 4.2) was added to stop the reaction.