Oximates dephosphorylation

Cnrrent work on dephosphorylation includes the use of different micellar systems. Scheme 10 illustrates dephosphorylation via novel functional detergents which contain an imidazole ring snbstitnted with an oxime or hydroxamic acid moiety. ... 

Depending on the specific organophosphate, some phosphorylated enzyme may be reactivated ("dephosphorylated") by certain oxime antidotes from one to two days after OP absorption. Thereafter a change in the nature of the enzyme-phosphoryl bond occurs, rendering the inactivation irreversible and necessitating the generation of new enzyme. 

In all the bimolecular reactions considered thus far the surfactant has been chemically inert, but a functionalized surfactant will generate a micelle in which reactant is covalently bonded (Scheme 3). The functional groups are basic or nucleophilic, and include amino, imidazole, oximate, hydroxamate, thiolate or hydroxyl [3-6,97-108]. In some cases comicelles of a functional and an inert surfactant have also been used. The reactions studied include deacylation, dephosphorylation, nucleophilic aromatic substitution, and nucleophilic addition to preformed carbocations, and some examples are shown in Scheme 7. 

However, as for reactions in non-functional micelles, sec , cannot be compared directly with second-order rate constants in water, whose dimensions are, conventionally, M /sec. But this comparison can be made provided that one specifies the volume element of reaction, which can be taken to be the molar volume of the micelles, or the assumed molar volume of the micellar Stern layer. This choice is an arbitrary one, but the volumes differ by factors of ca. 2 [107,108], so it does not materially affect the conclusions. The rate constants in the micelle for dephosphorylation, deacylation and nucleophilic substitution by a functional hydroxyethyl surfactant are similar to those in water [99], and similar results have been observed for dephosphorylation using functional surfactants with imidazole and oximate [106,107]. Similar results have been obtained by Fornasier and Tonalleto [108] for deacylation of carboxylic esters by a variety of functional comicelles. 

Certain oximes and atropine are used in pharmacological treatment of organophos-phate poisoning. While the oxime has the ability to dephosphorylate AChE and thus reactivate the enzyme, the mode of action of atropine, however, is different. Atropine acts... 

Bunton, C.A., Poroudian, H.J., GiUitt, N.D. Effects of headgroup structure on dephosphorylation of p-nitrophenyl diphenyl phosphate by functional oximate comiceUes. Langmuir 1999, 75(4), 1067—1074. 

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