[Activity of alpha-chymotrypsin immobilized in nanocapsules of poly(N,N-didodecyl-N,N-diallylammonium bromide)]

Biocatalytic nanocapsule systems containing alpha-chymotrypsin in the inner aqueous cavity were synthesized. These systems can function in both organic solvents and aqueous media. To this end, the reversed hydrated micelles of N,N-diallyl-N,N-didodecylammonium bromide (DDAB) in cyclohexane (w0 = 22) with alpha-chymotrypsin encapsulated were subjected to UV-induced polymerization. After precipitation with acetone, the nanocapsules were transferred into water with the use of AOT and subsequent sonication. The unilamellar liposomes thus formed have an inner monolayer from the polyDDAB network, an outer monolayer from the AOT molecules, and contain alpha-chymotrypsin in the inner aqueous medium. According to the light scattering data, the mean outer diameter of the nanocapsules is 20 nm. When compared with free enzyme in respect to p-nitrophenyl acetate hydrolysis, the alpha-chymotrypsin encapsulated in the liposomes exhibits the same K(m) value, but its values of kcat and of the inhibition constant by the reaction product Kp decreased by factors of 1.2 and 1.6, respectively. The alpha-chymotrypsin immobilized in the nanocapsules is thermally stable and catalytically active up to 80 degrees C. The polymer network hinders conformational rearrangements of the enzyme molecule upon heating.