title: Effects of micelles and vesicles on the oximolysis of p-nitrophenyl diphenyl phosphate: A model system for surfactant-based skin-defensive formulations against organophosphates.
abstract: The rates of oximolysis of p-nitrophenyl diphenyl phosphate (PNPDPP) by Acetophenoxime; 10-phenyl-10-hydroxyiminodecanoic acid; 4-(9-carboxynonanyl)-1-(9-carboxy-1-hydroyiminononanyl) benzene; 1-dodecyl-2-[(hydroxyimino)methyl]-pyridinium chloride (IV) and N-methylpyridinium-2-aldoxime chloride were determined in micelles of N-hexadecyl-N,N,N-trimethylammonium chloride (CTAC), N-hexadecyl-N,N-dimethylammonium propanesulfonate and dioctadecyldimethylammonium chloride (DODAC) vesicles. The effects of CTAC micelles and DODAC vesicles on the rates of oxymolysis of O,O-Diethyl O-(4-nitrophenyl) phosphate (paraoxon) by oxime IV were also determined. Analysis of micellar and vesicular effects on oximolysis of PNPDPP, using pseudophase or pseudophase with explicit consideration of ion exchange models, required the determination of the aggregate's effects on the pK(a) of oximes and on the rates of PNPDPP hydrolysis. All aggregates increased the rate of oximolysis of PNPDPP and the results were analyzed quantitatively. In particular, DODAC vesicles catalyzed the reaction and increased the rate of oximolysis of PNPDPP by IV several million fold at pH's compatible with pharmaceutical formulations. The rate increase produced by DODAC vesicles on the rate of oximolysis paraoxon by IV demonstrates the pharmaceutical potential of this system, since the substrate is used as an agricultural defensive agent and the surfactant is extensively employed in cosmetic formulations.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av Prof. Lineu Prestes 748, São Paulo, SP 05508 000, Brazil.
authors.forename: Larissa Martins
authors.initials: LM
authors.lastname: Gonçalves
authors.forename: Talita Guedes
authors.initials: TG
authors.lastname: Kobayakawa
authors.forename: Dino
authors.initials: D
authors.lastname: Zanette
authors.forename: Hernan
authors.initials: H
authors.lastname: Chaimovich
authors.forename: Iolanda Midea
authors.initials: IM
authors.lastname: Cuccovia
mesh_terms: D006868:Hydrolysis; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry; D008823:Micelles; D008956:Models, Chemical; D009574:Nitro Compounds / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D008081:Liposomes; D008823:Micelles; D009574:Nitro Compounds; D010091:Oximes; D010710:Phosphates; D013501:Surface-Active Agents; C518259:p-nitrophenyl diphenyl phosphate