sis. Acetylcholine esterase assay A 30 μl sample of red blood cell vesicles was mixed with an equal volume of buffer (20 mM Hepes, pH 7.6, 150 mM NaCl, 0.5 % Triton X-100), vortexed and incubated for 5 minutes at 37°C. Subsequently 640 μl sodium phosphate buffer (100 mM Na2PO4, pH 7.6), 50 μl DTNB (5,5'-dithiobis-(2-nitroben