Uphill transport of uranium across a liquid membrane

A liquid membrane was prepared by entrapping tributyl phosphate (TBP) in a cellulose triacetate (TAC) membrane matrix. The membrane was used to separate two aqueous solutions, one acidic and the other alkaline, which were saturated with TBP to prevent its loss from the membrane. Uphill transport of uranium was achieved with the TBP liquid membrane. Both solutions containing TBP were stirred magnetically. When the initial concentration of uranium in the two solutions was 3.5 mM, more than 50% of the uranium contained in the acidic solution was transported to the alkaline solution across the liquid membrane within 5 h. A transport mechanism is described in which the membrane-bound TBP acts as a mobile carrier for uranium.     

Ortho-selective direct cross-coupling reaction of 2-aryloxazolines and 2-arylimidazolines with aryl and alkenyl halides catalyzed by ruthenium complexes

The ortho position of the aromatic ring in 2-aryloxazolines and 2-arylimidazolines is selectively arylated and alkenylated with organic halides in the presence of a ruthenium(II)-phosphine complex. In the case of unsubstituted and para-substituted phenyloxazolines, 1:2 coupled products were obtained preferentially, while 1:1 coupled products were obtained in the case of meta-substituted phenyloxazolines and N-acylarylimidazolines. The reaction is proposed to proceed via the generation of an organoruthenium intermediate, formed by oxidative addition of the organic halide, and ortho-ruthenation directed by the coordination of the 2-oxazolinyl or 2-imidazolinyl group to the ruthenium center.     

Electrolytic process for regenerating nadp from nadph in a polymer matrix-bound form

Regeneration of nicotinamide adenine dinucleotide phosphate (NADP) from its reduced form (NADPH) was performed in a matrix-bound form by an electrolytic method. NADP was immobilized to alginic acid. No significant loss of coenzymic function was induced by the immobilization of NADP on the matrix. Bound NADP was soluble in water. Glucose-6-phosphate dehydrogenase (G-6-PDH) was taken as a model system of coenzyme requiring enzyme. G-6-PDH immobilized on alumina particles was coupled with the soluble form of bound NADP in a fluidized bed type of reactor. The enzymatically reduced coenzyme was electrolytically oxidized in the coenzyme regenerator of NADP from NADPH, which was found to cause no harmful loss of coenzymic function.     

Characteristics of NaI detector in positron imaging device HEADTOME employing circular ring array

In positron emission computed tomographs employing circular ring arrays of detectors, the performance of the imaging device has been specified ultimately by the characteristics of the detector. The responses of NaI detector were studied when detecting positron annihilation photon (511 keV). The study was mainly by using the NaI detector used in hybrid emission computed tomography (CT) "HEADTOME" we had developed. A series of measurements were carried out positioning two detectors with 40 cm distance and scanning 22Na point source in water. Both detectors was inclined from 0 degrees through 30 degrees to change incident angle of positron annihilation toward crystal face. Energy window was set from 100 to 700 keV. The results were presented as follows: Shortening the crystal length from 7 to 5 cm made sensitivity decrease about 10% and resolution deteriorate about 1 mm (FWHM). As the results of varying the width of the crystal, 20 mm width was optimal at any incident angle. The lead septum between the detectors was the thickness of 4 mm enough to reject multiple detector interactions (crosstalk). Beam mask which was made of lead in order to improve spatial resolution and placed on crystal face worked effectively for incident angles from 0 degrees to 15 degrees but degraded uniformity of spatial resolution from 0 degrees to through 30 degrees.     

Nonenzymatic regeneration of NADPH from nadp in water-soluble polymer matrix-bound form

In order to inhibit the dimerization during the electrolytic reduction of nicotinamide adenine dinucleotide phosphate (NADP), NADP was covalently attached to a water-soluble polymer at proper intervals. Matrix-bound NADP was found to exhibit coenzymatic functions comparable to that of free NADP when it was coupled with glucose-6-phosphate dehydrogenase. According to the polarographic behaviors, matrix-bound NADP was electrolytically reduced at a controlled potential of -1.8 V vs. saturated calomel electrode (SCE). The electrolytically reduced product was identified as the enzymatically active NADPH by means of spectrophotometric and enzymatic assays. The dimerization of radical (NADP ) during the electrolytic reduction might be significantly retarded by immobilizing NADP to a water-soluble polymer matrix.     

Highly luminescent glycocluster: silole-core carbosilane dendrimer having peripheral globotriaose

A novel glycocluster periphery functionalized by globotriaose (Galα1-4Galβ1-4Glcβ1-) possessing a silole moiety as a luminophor was synthesized. The photoluminescence spectrum of the glycocluster in pure water showed extremely strong emission at 475 nm. Analogous intense emission of the silole dendrimer was also observed in a lower water fraction of water/acetone mixture. The water fraction of the silole dendrimer solution strongly affected the emission intensity; however, these luminescences were constantly detected at around 475 nm.     

Development of KiBank, a database supporting structure-based drug design

KiBank is a database of inhibition constant (K_i) values with 3D structures of target proteins and chemicals. K_i values were accumulated from peer-reviewed literature searched via PubMed. The 3D structure files of target proteins were originally from Protein Data Bank (PDB), while the 2D structure files of the chemicals were collected together with the K_i values and then converted into 3D ones. In KiBank, the chemical and protein 3D structures with hydrogen atoms were optimized by energy minimization and stored in MDL MOL and PDB format, respectively.

KiBank is designed to support structure-based drug design. It provides structure files of proteins and chemicals ready for use in virtual screening through automated docking methods, while the K_i values can be applied for tests of docking/scoring combinations, program parameter settings, and calibration of empirical scoring functions. Additionally, the chemical structures and corresponding K_i values in KiBank are useful for lead optimization based on quantitative structure–activity relationship (QSAR) techniques.

KiBank is updated on a daily basis and is freely available at http://kibank.iis.u-tokyo.ac.jp/. As of August 2004, KiBank contains 8000 K_i values, over 6000 chemicals and 166 proteins covering the subtypes of receptors and enzymes.     

Cell-free protein synthesis by posterior silk gland polyribosome

Polyribosome was prepared from the posterior gland of silkworms, where silkfibroin is specifically synthesized. Coupled with the corresponding enzymes, amino acids, ATP and GTP, silkfibroin was produced in a cell-free system. The production of silkfibroin was monitored by SDS polyacrylamide gel electrophoresis of the dansylated polypeptides. The polysome fraction was adsorbed on DEAE Sephadex. Using the immobilized polysomes, a genetic information-transducing bioreactor for producing a specified protein was assembled. The promising features of this bioreactor are discussed.