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A water-in-oil microemulsion made up of a cetyltrimethylammonium bromide/n-butanol/isooctane/M II and Al III nitrate aqueous solution (M II = Mg or Ni or Zn) has been mixed with a microemulsion of the same composition but containing an ammonia solution instead of a metal nitrate solution. Collisions between the reverse micelles containing an M II and Al III solution and those containing an NH 3 solution form short-lived dimers that act as reaction vessels and control the nucleation and growth of MgAl, NiAl or ZnAl hydrotalcitelike compounds (HTlcs). The double water-in-oil microemulsion technique yields colloidal dispersions of nanoparticles whose size and shape were examined by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The colloidal particles were between 50 and 100 nm depending on the composition of the microemulsions (water-tosurfactant and oil-to-water molar ratios). The separation of the nanoparticles from the reaction medium produces a gel

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(R)-4-Hydroxy-, -4-fluoro-, -4-bromo-, and -4-iodo[2.2]paracyclophanes have been prepared and their absolute configuration assigned on the basis of chemical correlations. Different relationships between the specific optical rotation and the group polarizability have been found depending on the ability of the substituents to conjugate with the aromatic ring. At least for 4,7-disubstituted [2.2]paracyclophanes, the effects of the substituents on the specific rotation seem to be additive, independent of the wavelength used. An equation has been derived which allows to predict, to a satisfactory approximation, the [α] values of 4-X-7-methyl[2.2]paracyclophanes whenever the group polarizability of the substituents is known.

The adsorption of myoglobin (Mb) onto nanosized nickel aluminum hydrotalcite (NiAl-HTlc) surface was studied, and the structural properties of the resulting protein layer were analyzed by using FT-IR, Raman, and fluorescence spectroscopies. Upon adsorption onto the nanoparticle surface, the protein molecules maintained their secondary structure, while the tertiary structure was altered. The fluorescence spectra and anisotropy values of adsorbed Mb revealed that the emitting amino acid residues are affected by different microenvironments when compared to the native protein behavior. Moreover, the decrease of fluorescence decay times of tryptophan indicated the occurrence of interactions among the fluorophores and the constituents of the nanoparticles, such as the metal cations, which can take place when conformational changes of Mb occur. Raman spectra indicated that the interaction of Mb molecules with NiAl-HTlc nanoparticles modified the porphyrin core, changing the spin state of the heme iron from high spin (HS) to low spin (LS). The enzymatic activity of the nanostructured biocomposite was evaluated in the oxidation of 2-methoxyphenol by hydrogen peroxide and discussed on the basis of structural properties of adsorbed myoglobin.

Biocomposites with enzymatic activity were obtained by adsorption of lipase from Candida rugosa on the surface of different layered zirconium phosphates and phosphonates such as R-zirconium hydrogenphosphate, solid dispersions of zirconium phosphate in silica, zirconium carboxyethanephosphonate, zirconium phosphate-carboxyethanephosphonate, zirconium benzenephosphonate, and zirconium phosphatebenzenephosphonate. All the supports were characterized for chemical composition, BET specific surface area, surface ion exchange capacity, and X-ray diffraction patterns. The adsorption process at 4 °C was studied as a function of time of equilibration of the support with the lipase solutions (0.5 mg/mL) and as a function of the amount of protein present in the equilibrating solution. The activities of biocomposites with the different supports, at different protein loadings, were obtained by determining the amount of acetic acid produced by catalyzed hydrolysis of p-nitrophenylacetate. The best results in terms of protein surface adsorption (29 mg of protein/g of support) and of catalytic efficiency (95%) were achieved with hydrophobic supports based on zirconium benzenephosphonate. The biocomposites can be stored for more than one month at 4 °C without loss of enzymatic activity, have been used in several cycles, and undergo limited thermal degradation when used at 40 °C.

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Decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate ion is speeded more b y small assemblies of didodecyl(dimethyl)ammonium chloride (DDDACI) than b y fully formed assemblies or b y normal cationic micelles. The first-order rate constants, FM, of reaction of fully micelle-bound substrate increase with decreasing surface charge density of normal cationic micelles with a change from hydrophilic to less hydrophilic counter-ions, e.g., in going from CTAOH to CTAOTos (CTA = C, , H, , NMe, and Tos = toluene-p-sulphonate), or from cationic to zwitterionic micelles. These changes are ascribed to changes in transfer free energies of the initial-state carboxylate ion and the chargedelocalized transition state so that small assemblies of cationic amphiphiles, e.g., of D D D A or (C,H,,),N +R, are better catalysts than cationic micelles because of less initial-state stabilization. A similar explanation can be applied to catalysis of decarboxylation b y synthetic cationic vesicles.