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.     

A general strategy to determine a target DNA sequence of a short peptide: application to a d-peptide.

Short peptides could potentially provide a novel element to read-out DNA sequences from the major groove. However, it is difficult to determine sequence-preference of de novo designed monomeric short peptides. Because DNS-binding affinity and specificity of short peptides are usually much lower than those of native DNA-binding proteins, determining the sequence-preference of short peptides by conventional methods utilized to deduce the target sequence of proteins often produces an unclear outcome. We report here a general strategy to defining the sequence-preference of a DNA-binding short peptide by using the heterodimers. A GCN4 basic region peptide tethers a low-affinity DNA-binding peptide adjacent to a GCN4 binding sequence through the cyclodextrin-adamantane association, thereby increasing local concentration of the low-affinity peptide on degenerated DNA sequences. An increase of the local concentration allows one to select a preferential sequence for the low-affinity DNA binding peptide. The method successfully identified specific sequences of short peptides derived from native DNA-binding proteins. The usefulness of this approach has been demonstrated by identifying preferred DNA targets for a peptide composed only of d-amino acids. The method is potentially applicable not only to artificial peptides, but also to other synthethic ligands.     

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.     

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.     

Preparation and properties of polyamides and polyimides containing phenoxathiin units

Novel polyimides and polyimides having phenoxathiin units have been prepared. Polyamides with inherent viscosities in the range of 0.5–2.9 were readily prepared by the polycondensations of phenoxathiin diamines with aromatic diacyl chlorides and of aromatic diamines with new phenoxathiin diacyl chlorides. The polyimides were synthesized from phenoxathiin diamines and pyromellitic dianhydride by using a two-step procedure. The polyamic acids which formed in the first step had inherent viscosities ranging from 1.0 to 1.6, and they were converted to the polyimides by thermal cyclodehydration. Some of the phenoxanthiin-containing polyamides were highly soluble in polar amide solvents and dimethyl sulfoxide. A series of novel polymers containing phenoxathiin units were much more thermostable than the corresponding polymers having open-chain diphenyl ether linkages.     

Stress and Cracks in Gel-Derived Ceramic Coatings and Thick Film Formation

Residual stress was evaluated by measuring the substrate curvature for alkoxide-derived silica and titania films deposited on silica glass substrates. The residual stress was tensile, increasing with increasing heat-treatment temperature. The stress in fired films was affected greatly by water/alkoxide ratio and chelating agents in starting solutions. Secondly, in situ observation was made on cracking of gel films subjected to heat-treatment. Silica and titania gel films deposited on silicon wafers were cracked in the heating-up stage at temperatures of 100°–400°C, depending on the film thickness and heating rate. Larger thickness and lower heating rates were found to lower the cracking onset temperature. Finally, organic polymers with amide groups were demonstrated to increase the uncracking critical thickness. The polymers include polyvinylpyrrolidone and polyvinylacetamide, allowing single layer ceramic coating films over 1 m in thickness to be formed without cracking.     

Studies on the stereochemical course of intramolecular cycloaddition reactions of olefinic o-quinodimethanes-stereoselective synthesis of 8α, 9α, 14β-estranes

The stereoselective synthesis of 3-O-methyl-7α-$\text{p}$-toluenesulphonyl-8α, 9α, 14β-estradiol ($\text{25}$) and its 11-oxo derivative ($\text{26}$) $\text{via}$ thermolysis of 1β-$\text{tert}$-butoxy-2α-[2-(4-methoxybenzocyclobutenyl)ethyl]-2β-methy1-3α-[2-($\text{p}$-toluenesulphonyl)ethenyl] cyclopentane ($\text{22}$) and its oxo derivative ($\text{24}$), which were derived from condensation product ($\text{9}$) of optically active aldehyde ($\text{8}$) and 1-cyano-4-methoxybenzocyclobutene through $\text{10}$ and $\text{11}$ to selenides $\text{16}$ and $\text{21}$, is described.