Iodosobenzoate-Functionalized Surfactant Vesicles: Adjustable Reactivity in Reactive Phosphate Cleavage

摘要

The imidazole-functionalized, zwitterionic phosphatidylcholine surfactant 1 displayed unusual kinetic behavior. Native vesicles of 1 were quite unreactive in the cleavage of (e.g.) p-nitrophenyl hexanoate, whereas 1:2 covesicles of 1 and N.N-dihexadecyldimethyl-ammonium bromide, 2, were more than 200 times as reactive. We suggested that the reactivity of vesicular 1 was controlled by the accessibility of its imidazole groups to the substrate. In native vesicles, strong N+/-O-P electrostatic interactions between adjacent surfactant head groups pinned them and their pendant imidazole moieties to the vesicular surface, mitigating their reactivity. Covesicallization with cationic 2, however, neutralized these interactions, freed the imidazole moieties, and potentiated their reactivity. We report that the iodosobenzoate-functionalized vesicles constructed from zwitterionic surfactant 3 manifest analogous adjustable reactivity. In view of the importance of iodosobenzoate reagents for the catalytic cleavage of toxic phosphates, we demonstrate the action of covesicular 3/2 against the simulant substrate, p-nitrophenyldiphenyl phosphate (PNPDPP). The reactivity of vesicular iodosobenzoate surfactant 3 toward p-nitrophenyldiphenyl phosphate is strongly potentiated in covesicles with dihexadecyldimethylammonium bromide. Reprints. (aw)