Determination of haloalkane dehalogenase activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of haloalkane dehalogenase activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of product - bromide or chloride ions - was monitored by sequential capillary zone electrophoresis runs. The determinations were performed in a 75 microm fused-silica capillary using 5 mM chromate, 0.5 mM tetradecyltrimethylammonium bromide (pH 8.4) as a background electrolyte, separation voltage 15 kV (negative polarity) and indirect detection at sample wavelength 315 nm, reference wavelength 375 nm for brominated and chlorinated substrates, respectively 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity) and direct detection at 200 nm for brominated substrates. The temperature of capillary was in both cases 25 degrees C. The method is rapid, can be automated, and requires only small amount of enzyme preparation and substrate.     

Approximation of convex bodies by simplices

This paper deals with the following kind of approximation of a convex bodyQ in Euclidean space E ⁿ by simplices: which is the smallest positive numberh _S(Q) such thatS ₁ Q S ₂ for a simplexS ₁ and its homothetic copyS ₂ of ratioh _S(Q). It is shown that ifS ₀ is a simplex of maximal volume contained inQ, then a homothetic copy ofS ₀ of ratio 13/3 containsQ.     

EPR in non-doped irradiated polyacetylene

The influence of -irradiation on the paramagnetic properties of non-doped polyacetylene at low and high radiation doses has been studied and summarized. The dependence of the EPR spectra on the radiation dose in irradiated polyacetylene has been measured. No essential changes of the spin mobility as a consequence of irradiation were observed. Our measurements of spin concentration confirm the high resistivity of non-doped polyacetylene to radiation.     

A model of solidification under microgravity conditions

The influence of the microgravity environment on solidification processes is discussed. A simple model of the solidification of a binary-alloy is presented with the chemical diffusion influenced by the gravitational field. Using the results of Mullins and Sekerka, we employ the linear theory of hydrodynamic stability to investigate the interfacial instability driving the pattern-forming processes in solidification. As a result, we estimate the characteristic size of the elements of the emerging pattern. We show that, in spite of good agreement of our result with the size of cellulae observed in experiments, the model cannot explain the changes in the patterns occurring in space environment. In conclusion we shortly discuss the possibility of adding realism to our simple model by including the effect of convection.     

A microcomputer-controlled titrator for automated individual analysis

A titration unit for automatic analysis systems is described. The titrator performs different titrations specified by strings of digital parameters. It has 4 independent titration stations with individual electrode systems. A multiburette with 20 cylinders provides all stations with the necessary reagents. End-point titrations, and incremental and equilibrium titrations are controlled by a microcomputer. In combination with a sample transport and a desk calculator, the titrator can be used to process automatically samples of different natures which require different treatment.     

2,8'-disubstituted-1,1'-binaphthyls: a new pattern in chiral ligands

The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product).