Novel Carboxyl Esterase Preparations for the Resolution of Linalyl Acetate

 Biocatalytic resolution of the tertiary terpene alcohol (±)-linalool was accomplished via hydrolysis of its corresponding acetate ester using two highly enantiospecific enzymes (E > 100). The latter were identified in a crude cell-free extract of Rhodococcus ruber DSM 43338 and could be separated by (partial) protein purification. Since they showed opposite enantiopreference, they were termed (R)- and (S)-linalyl acetate hydrolase (LAH). The activity and selectivity of the enzyme preparations was markedly dependent on the fermentation conditions.     

High‐Resolution Separation of Oligo(acrylic acid) by Capillary Zone Electrophoresis

Summary: Oligo(acrylic acid)s, produced by RAFT polymerization, have been separated and analyzed for the first time by capillary zone electrophoresis. The resolution obtained by capillary electrophoresis in borate buffers is far higher than that currently achieved using size exclusion chromatography. This work demonstrates that capillary electrophoresis is the technique of choice for the characterization of oligomers of acrylic acid and of other water‐soluble monomers involved in emulsion polymerization processes.

Electropherograms of different acrylic acid (AA) oligomers obtained by CZE.     

A validated RP‐HPLC method for the evaluation of the influence of grapefruit juice on liver S9 activation of sacubitril

Grapefruit juice inhibits esterase enzyme. Therefore, a possible interaction with ester prodrugs should be taken into consideration. In this study, the influence of grapefruit juice on sacubitril (SAC) rat liver S9 activation by esterase enzyme was evaluated. An RP‐HPLC method was developed and validated for estimation of SAC in rat liver S9 fraction using a C₁₈ Cyano column as stationary phase and acetonitrile–sodium di‐hydrogen phosphate buffer (0.02 m , pH 4 adjusted by o‐phosphoric acid, 40:60, v/v), as mobile phase at a flow rate of 1 mL/min and UV detection at 254 nm. The method was successfully applied to an in vitro study in which SAC was incubated with rat liver S9 fraction prepared from rats that had previously ingested grapefruit juice for a week. The calculated SAC concentration after incubation was compared with that of SAC incubated with rat liver S9 fraction from the rat control group. The statistical significance between the results of test and control incubation sets was assessed. In conclusion, the current study demonstrated that grapefruit juice decreased SAC hydrolysis, hence delaying its activation to sacubitrilat (active form) in gut lumen. Based on this food–drug interaction, it may be required that grapefruit juice should be consumed with caution in patients receiving SAC.     

Spontaneous Edge Currents for the Dirac Equation in Two Space Dimensions

Spontaneous edge currents are known to occur in systems of two space dimensions in a strong magnetic field. The latter creates chirality and determines the direction of the currents. Here we show that an analogous effect occurs in a field-free situation when time reversal symmetry is broken by the mass term of the Dirac equation in two space dimensions. On a half plane, one sees explicitly that the strength of the edge current is proportional to the difference between the chemical potentials at the edge and in the bulk, so that the effect is analogous to the Hall effect, but with an internal potential. The edge conductivity differs from the bulk (Hall) conductivity on the whole plane. This results from the dependence of the edge conductivity on the choice of a selfadjoint extension of the Dirac Hamiltonian. The invariance of the edge conductivity with respect to small perturbations is studied in this example by topological techniques Mathematics Subject Classification (2000). 81Q10, 58J32     

Steric control of substituted phenoxide ligands on product structures of uranyl aryloxide complexes

A series of uranyl aryloxide complexes has been prepared via metathesis reactions between [UO(2)Cl(2)(THF)(2)](2) and di-ortho-substituted phenoxides. Reaction of 4 equiv of KO-2,6-(t)()Bu(2)C(6)H(3) with [UO(2)Cl(2)(THF)(2)](2) in THF produces the dark red uranyl compound, UO(2)(O-2,6-(t)()Bu(2)C(6)H(3))(2)(THF)(2).THF, 1. Single-crystal X-ray diffraction analysis of 1 reveals a monomer in which the uranium is coordinated in a pseudooctahedral fashion by two apical oxo groups, two cis-aryloxides, and two THF ligands. A similar product is prepared by reaction of KO-2,6-Ph(2)C(6)H(3) with [UO(2)Cl(2)(THF)(2)](2) in THF. Single-crystal X-ray diffraction analysis of this compound reveals it to be the trans-monomer UO(2)(O-2,6-Ph(2)C(6)H(3))(2)(THF)(2), 2. Dimeric structures result from the reactions of [UO(2)Cl(2)(THF)(2)](2) with less sterically imposing aryloxide salts, KO-2,6-Cl(2)C(6)H(3) or KO-2,6-Me(2)C(6)H(3). Single-crystal X-ray diffraction analyses of [UO(2)(O-2,6-Cl(2)C(6)H(3))(2)(THF)(2)](2), 3, and [UO(2)Cl(O-2,6-Me(2)C(6)H(3))(THF)(2)](2), 4, reveal similar structures in which each U atom is coordinated by seven ligands in a pseudopentagonal bipyramidal fashion. Coordinated to each uranium are two apical oxo groups and five equatorial ligands (3, one terminal phenoxide, two bridging phenoxides, and two nonadjacent terminal THF ligands; 4, one terminal chloride, two bridging phenoxides, and two nonadjacent terminal THF ligands). Apparently, the phenoxide ligand steric features exert a greater influence on the solid-state structures than the electronic properties of the substituents. Emission spectroscopy has been utilized to investigate the molecularity and electronic structure of these compounds. For example, luminescence spectra taken at liquid nitrogen temperature allow for a determination of the dependence of the molecular aggregation of 3 on the molecular concentration. Electronic and vibrational spectroscopic measurements have been analyzed to examine trends in emission energies and stretching frequencies. However, comparison of the data for compounds 1-4 reveals that the innate electron-donating capacity of phenoxide ligands is only subtly manifest in either the electronic or vibrational energy distributions within these molecules.