Purification Methods
Triturate this zwitterionic detergent (~50g) with MeOH (200ml), then triturate it with Me2CO (500mL), collect it by vacuum filtration and dry it thoroughly at ~20o. Recrystallise it at 0o from absolute MeOH followed by drying in vacuo to constant weight. It should give one spot with RF 0.32 by TLC on silica gel G in 95% MeOH/5% NH4OH and visualized with iodine vapour; the tertiary amine precursor has RF 0.40. It has low UV absorption (1% in H2O: A280nm is 0.029 and A260nm is 0.035), and the CMC (critical micellar concentration) is 8mM. It is soluble in H2O, MeOH, Me2SO but insoluble in Me2CO, MeCN, hexane, toluene and xylene. [Hjelmeland et al. Anal Biochem 130 72 1983, Matuo et al. Methods Enzymol 198 155 1991.] CHAPSO (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate betaine) [82473-24-3] M 630.89, m 184-196o, [ ] D +19o (c 2, H2O), pKEst (1) ~<2 (acidic), pKEst(2) ~9 (basic). Dissolve this zwitterionic detergent (~ 60g) in 40% aqueous MeOH and stir it with the mixed-bed ion-exchange resin RG-501 x 8 (100g, Bio-Rad) until the pH of the supernatant is ~ 7. Filter off the resin and evaporate the filtrate to dryness under reduced pressure. Check for homogeneity by TLC on silica gel G in 95% MeOH/5% NH4OH and visualize the spot with iodine vapour (see CHAPS above). [Hjelmeland et al. Anal Biochem 130 72 1983, Matuo et al. Methods Enzymol 198 155 1991.]
