It has been suggested to use surfactant mrcelles as mrcrocontamers for mcreasmg the efficiency of neurolephc targeting from blood flow mto the bram The neuroleptrc actron of halopendol, mtrapentoneally injected mto mtce m mmellar solutron of non-iomc block copolymer surfactant (pluromc P-85) m water, increased several-fold tf compared with that observed for halopendol aqueous solutron Incorporatron of bram-specific antibodies mto halope~dol~onta!nlng mtcelles resulted m addrtronal drasuc increase (more than by 2 orders of magnitude) m the drug effect Neuroleptrcs, Haloperrdol, Hematoenceph~lc barrter, Directed transport, Mtcelle, Pluromc P-85

A kinetic theory is proposed for enzymatic reactions proceeding in reversed micellar systems in organic solvents, and involving SUbStrdteS capable of partitioning among all pseudophases of the micellar system, i.e. aqueous cores of reversed micelles, micellar membranes and organic solvent. The theory permits determination of true (i.e. with reference to the aqueous phase, where solubilized enzyme is localized) catalytic parameters of the enzyme, provided partition coefficients of the substrate between different phases are known. The validity of the kinetic theory was verified by the example of oxidation of aliphatic alcohols catalyzed by horse liver alcohol dehydrogenase in the system of reversed sodium bis(2-ethylhexyl)sulfosuccinate (AOT, aerosol OT) micelles in octane. In order to determine partition coefficients of alcohols between phases of the micellar system, flow microcalorimetry technique was used. It was shown that in the first approximation, the partition coefficient of the substrate in a simple biphasic system consisting of water and corresponding organic solvent can be used as an estimate for the partition coefficient of the substrate between aqueous and organic solvent phases of the micellar system. True values of the Michaelis constant of alcohols in the micellar system, determined using suggested approach, are equal to those obtained in aqueous solution and differ from apparent values referred to the total volume of the system. The results clearly show that the previously reported shift in the substrate specificity of HLADH, observed on changing from aqueous solution to the system of reversed aerosol OT micelles in octane, is apparent and can be explained on the basis of partitioning effects of alcoholic substrates between phases of the micellar system. Micellar enzymology, which deals with enzymes entrapped in surfactant reversed micelles in orgarlic solvents, has received increasing attention during the last decade (for recent reviews see [l -41). The kinetic description of enzymatic reactions in reversed micellar systems often represents a rather complicated problem because of the microheterogeneity of the micellar medium: micellar solution is composed of tiny surfactantstabilized aqueous microdroplets (with diameter up to 200 nm) suspended in organic solvent. Solubilized enzyme molecules are localized exclusively inside these droplets (micelles), whereas the substrate can be distributed throughout the whole volume of the system. Evidently, the latter fact should be taken into account in kinetic analysis. To allow for substrate partitioning, the pseudophase approach can be used, according to which micellar systems can be regarded as being composed of two phases, namely the phase of organic solvent and a pseudophase of micelles. The pseudophase approach was successfully used for description of the kinetics of nonenzymatic [5] as well as enzymatic [6 -91 reactions in micellar systems. However, the notion that a micellar solution can be viewed as a pseudobiphasic system is to a certain extent on ...

Micellar enzymology, a new trend in molecular biology, studies the catalysis by enzymes entrapped into hydrated reversed micelles of surfactants (detergents, phospholipids) in organic solvents. The effect of solubilization on enzymatic properties is briefly considered. Applications of such biocatalytic systems in fine organic syntheses, in clinical and chemical analyses, and in medicine, as well as probable future trends in biotechnology are discussed.

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The catalytic activity and stability of laccase in the detergentless ternary system hexane - 2-propanol - water were studied. In the microemulsion region of the phase diagram the enzyme exhibited the highest catalytic activity and stability, which were comparable to those in aqueous solution. The character of the microenvironment inside microemulsion droplets was studied using nitrate anion as spectral probe and its polarity was found to correspond to that of 75% v/v aqueous 2-propanol. In principle, laccase can be recovered many times from the microemulsion without loss of catalytic activity.

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