High-efficiency and minimum-waste continuous kinetic resolution of racemic alcohols by using lipase in supercritical carbon dioxide

A novel continuous-flow scCO(2) process for kinetic resolution of racemic alcohols can be performed with an immobilized lipase to lead to a quantitative mixture of the corresponding optically active acetates with up to 99% ee and unreacted alcohols with up to 99% ee, in which the productivity of the optically active compounds was improved by over 400 times compared to the corresponding batch reaction using scCO(2).     

Preparation of copoly(vinyl alcohol-styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. III. Kinetic analysis of the catalysis

Hydrolysis of dextrin in the presence of copoly(vinyl alcohol-styrenesulfonic acid) resin was investigated kinetically. The hydrolysis rate increased nearly proportionally with increases in the concentrations of the substrate and the catalyst copolymer. This is in contrast to the results found in a similar homogeneous reaction in the presence of soluble copoly(vinyl alcohol–styrenesulfonic acid) in which the reaction rate clearly followed Michaelis–Menten type kinetics. However, the hydrolysis was inhibited by the addition of copoly(vinyl alcohol–styrene) resin or poly(vinyl alcohol). Activation parameters of the hydrolysis in the presence of the copolymer resin as catalyst were also investigated, and it was found that the enthalpy and entropy of the activation in the presence of the copolymer resin were lower than those in Amberlite 120B and slightly decreased when vinyl alcohol unit was introduced. From these results it was concluded that the poly(vinyl alcohol) sequence introduced into the insoluble catalyst copolymer resin also played an important part in the acceleration of dextrin hydrolysis in a manner similar to the case of a soluble catalyst, although the interaction with the substrate was weaker.     

THEORETICAL STUDY OF COLOR CONTROL MECHANISM IN RETINAL PROTEINS.: I. ROLE OF THE TRYPTOPHAN RESIDUE, TYROSINE RESIDUE AND WATER MOLECULE

Abstract: We calculated the opsin shift due to the electrostatic interaction between tryptophan or tyrosine residues and the chromophore by the perturbation method for various mutual configurations. The obtained opsin shift maps for these configurations demonstrated that when the above residues reside around the ionone ring side, the positive opsin shift (bathochromic shift) is obtained, and when they reside around the Schiff-base side, the negative opsin shift (hypsochromic shift) is obtained. These properties hold true, irrespective of the orientation of those residues, indicating that higher order multipoles of the group play a central role. The maximum value of the opsin shift by these groups amounts to several hundred wavenumbers. These results indicate that the location of some of those amino acid residues at proper positions around the chromophore can cause a considerable opsin shift. We also calculated opsin shift maps for the various mutual configurations between a water molecule and the chromophore for comparison.     

Graft copolymerization of methyl methacrylate to poly(vinyl alcohol) initiated by ferric ion-hydrogen peroxide system

The reaction occurring on treatment of samples of poly(vinyl alcohol) previously oxidized by sodium hypochlorite with ferric ion and hydrogen peroxide was studied. The graft copolymerization taking place on adding methyl methacrylate to the above system was also studied. Early in the reaction there was a period during which hydrogen peroxide was greatly reduced by the poly(vinyl alcohol), and this corresponded with a rapid cleavage reaction of the main chain of the polymer. Moreover, it was found that the reaction was quantitatively proportional to the formation of carbonyl groups in the sample. On the other hand, very few grafts were scarcely formed during this period; they formed by a mild reaction which took place immediately after this period. It seems that this behavior is quite different from that observed with the ceric ion initiating system. It is presumed that the formation of grafts is due to radicals formed by the cleavage of the main chain, and that the structure of the copolymer so formed is something like a block polymer.     

Particle monolayer formation at the air–water interface by silica particle with well‐defined grafted polymer

Particle monolayer formation at the air–water interface by polymer‐grafted colloidal silica was investigated. Methyl methacrylate (MMA) was polymerized from initiative bromide groups at colloidal silica surface by atom transfer radical polymerization. We obtained polymer‐grafted silica particle (SiO₂‐PMMA) with relative narrow polydispersity of PMMA. For the polymer‐grafted particle with high graft density, particle monolayer formation was confirmed by π‐A isotherm measurement and SEM observation. Interparticle distance was controllable by surface pressure. Furthermore, grafted polymer chains were suggested to be fairly extended at the air–water interface. However, for the polymer‐grafted particle with low graft density, monolayer structure on substrate showed aggregation and voids. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2789–2797, 2006     

Spatially-resolved observation of glow discharge plasma for atomic emission spectrometry.

An imaging spectrograph equipped with a CCD detector was employed to measure two-dimensional emission images from a glow discharge plasma in atomic emission spectrometry. The emission images at Zn I 334.50 nm for a zinc sample and at Cu I 324.75 nm for a copper sample could be obtained. Their emission intensities were not uniform in the radial direction of the plasma region but became weaker at larger distance from the central zone. The two-dimensional distribution would result from a spatial variation in the excitation efficiency of the plasma and thus provide useful information for understanding the excitation processes occurring in the plasma.     

High preconcentration of ultra-trace metal ions by liquid–liquid extraction using water/oil/water emulsions as liquid surfactant membranes

A high preconcentration method by liquid–liquid extraction using liquid surfactant membranes was developed. The water-in-oil (w/o) emulsion containing dilute hydrochloric acid, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (PC-88A), liquid paraffin, and kerosene was used for the extraction. In a resulting volume of 1000 cm³ of an aqueous sample solution (pH 5.0) containing less than 1 mg of each metal ion, 2 cm³ of w/o emulsion droplets coated with sorbitan monooleate were dispersed. The analyte metal ions in the outer bulk aqueous phase were extracted into the organic phase to form a complex with PC-88A and successively back-extracted into the inner aqueous phase. The analytes in the resulting inner aqueous phase were determined subsequently by graphite furnace atomic absorption spectrometry applied as a detector. By this procedure, concentration factors of 570, 820, 750, 970, 860, and 880 were achieved for chromium(III), manganese(II), cobalt(II), nickel(II), copper(II), and cadmium(II), respectively, and also the respective detection limits (3σ) of 0.4, 20, 1.2, 18, 18, and 0.7 pg cm⁻³ were obtained.