Synthesis of novel chitosan resin derivatized with serine moiety for the column collection/concentration of uranium and the determination of uranium by ICP-MS

A chitosan resin derivatized with serine moiety (serine-type chitosan) was newly developed by using the cross-linked chitosan as a base material. The adsorption behavior of trace amounts of metal ions on the serine-type chitosan resin was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The resin could adsorb a number of metal cations at pH from neutral to alkaline region, and several oxoanionic metals at acidic pH region by an anion exchange mechanism. Uranium and Cu could be adsorbed selectively at pH from acidic to alkaline region by a chelating mechanism; U could be adsorbed quantitatively even at pH 3–4. Uranium adsorbed on the resin was easily eluted with 1 M nitric acid: the preconcentration (5-, 10-, 50- and 100-fold) of U was possible. The column treatment method was used prior to the ICP-MS measurement of U in natural river, sea and tap waters; R.S.D. were 2.63, 1.13 and 1.37%, respectively. Uranium in tap water could be determined by 10-fold preconcentration: analytical result was 1.46±0.02 ppt. The resin also was applied to the recovery of U in sea water: the recovery tests for artificial and natural sea water were 97.1 and 93.0%, respectively.     

Robust and simple interface for microchip electrophoresis-mass spectrometry

A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of the microchip. The spray nozzle was attached to the microchip using a polyether ether ketone screw without adhesive, thus allowing easy replaced. Sample injection and electrophoretic separation was performed by control of the voltage only. The analysis of a few basic drugs was performed using the optimized MCE-MS system. The separation was improved by using a high-viscosity separation buffer and a spray nozzle with a small bore size. This system was also applied to the separation of peptides and protein-trypsin digests. Sample adsorption was minimized by adding acetonitrile to the separation buffer when using a quartz microchip.     

Synthesis of poly (ethylene oxide)-b-polysilane by anionic polymerization of masked disilenes using a macroinitiator method

Poly(ethylene oxide-)-poly(1, 1-dimethyl-2, 2-dihexyldisilene) block copolymers (PEO-b-PMHS) were synthesized by the anionic polymerization of masked disilenes initiated with the potassium alkoxide of poly(ethylene glycol). The block copolymer self-assembled into polymer micelles in water accompanied by a transition in the polysilane conformation.     

Synthesis of microspheres with microphase‐separated shells

Novel structural microspheres of the Janus type, with microphase‐separated polystyrene (PS) and poly(tert‐butyl methacrylate) (PBMA) shells and crosslinked poly(2‐vinyl pyridine) (PVP) cores, were synthesized with the crosslinking of PVP spherical domains in poly(styrene‐block‐2‐vinyl pyridine‐block‐tert‐butyl methacrylate) ABC triblock terpolymer film with PS/PBMA lamellae–PVP spherical structures. For the formation of lamellae‐sphere structures, toluene, which was a selective solvent for the ABC triblock terpolymer, was used. With the crosslinking of PVP spheres in the microphase‐separated film with 1,4‐diiodobutane gas, the microphase structure of the terpolymer was fixed, and microspheres composed of microphase‐separated PS and PBMA shells and P2VP cores were obtained. The size distribution of the purified microspheres was narrow. The characteristics of the microspheres and their aggregation behaviors in selective solvents were investigated by transmission electron microscopy and light scattering methods. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2091–2097, 2000     

Synthesis of block‐graft polymers by anionic polymerizations

Two poly(4‐methylstyrene) (P4MS)‐block‐polystyrene (PS)‐block‐P4MS triblock copolymers were prepared by successive anionic addition of styrene and 4‐methylstyrene monomers as the core backbone ( CB ) for the architecture of block‐graft polymers. Both terminal 4‐methylstyrene blocks of CB were metalated with a sec‐butyllithium (sec‐BuLi)/tetramethylethylenediamine (TMEDA) complex in cyclohexane. The first‐generation block‐graft polymer ( 1BG ) was prepared by anionic polymerization of α‐methylstyrene by the lithiated CB in tetrahydrofuran (THF) at –78°C and subsequently the terminal graft ends were capped with a small amount of 4‐methylstyrene. The characterization of those block‐graft polymers was carried out in detail.     

Synthesis of a Photoaffinity‐Labeled (11Z)‐Retinal: Identification of Retinal/Rhodopsin Cross‐Linked Sites along the Visual‐Transduction Path

The retinal chromophore (11Z)‐3‐diazo‐4‐oxoretinal ( 1 ) with two photo‐labile moieties has been synthesized by semi‐hydrogenation of an 11‐yne precursor with activated Zn in aqueous media. Incorporation of 1 into opsin yielded diazoketo rhodopsin (DK‐Rh), which, upon bleaching, gave rise to intermediates batho‐Rh, lumi‐Rh, meta‐Rh, and meta‐II‐Rh corresponding to those of native Rh but at lower temperatures. Photoaffinity labeling of DK‐Rh and these bleaching intermediates showed that the ionone ring cross‐linked to Trp265 of helix F in DK‐Rh and batho intermediate, and to Ala169 of helix D in lumi, meta‐I, and meta‐II intermediates. These results demonstrate the occurrence of large conformational changes along the visual transduction path, which, in turn, is responsible for activation of the G‐protein.     

2-Substituted thiazole-4-carboxamide derivatives as tiazofurin mimics: synthesis and in vitro antitumour activity

Tiazofurin analogues bearing a 5-hydroxymethyl-2-methyl-tetrahydrofuro[2,3-d][1,3]dioxol-6-ol moiety as a sugar mimic (2 and 3), and two novel thiazole-based acyclo-C-nucleosides 4 and 16 have been synthesized in multistep sequences starting from d-xylose (compounds 2 and 3) or from d-arabinose (compounds 4 and 16). All synthesized analogues showed potent in vitro antitumour activities against a panel of human tumour cell lines. Flow cytometry data suggest that cytotoxic effects of analogues 2–4 and 16 in the culture of K562 cells might be mediated by apoptosis. It was also found that these analogues induced changes in cell cycle distribution of K562 cells. Results of western blot analysis (upregulation of Bax and downregulation of Bcl-2, activation of caspase-3 and the presence of a PARP cleavage product) suggest that tiazofurin mimics (2–4 and 16) in K562 cells induced apoptosis in a caspase-dependent way.     

Development of a fluoride-responsive amide bond cleavage device that is potentially applicable to a traceable linker

A fluoride-responsive (FR) amino acid that induces amide bond cleavage upon the addition of a fluoride was developed, and it was applied to an FR traceable linker. By the use of an alkyne-containing peptide as a model of an alkynylated target protein of a bioactive compound, introduction of the FR traceable linker onto the peptide was achieved. Subsequent fluoride-induced cleavage of the linker followed by labeling of the released peptide derivative was also conducted to examine the potential applicability of the FR traceable linker to the enrichment and labeling of alkynylated target molecules.     

Cross‐Conjugated Hexaphyrins and Their Bis‐Rhodium Complexes

A cross‐conjugated hexaphyrin that carries two meso‐oxacyclohexadienylidenyl (OCH) groups 9 was synthesized from the condensation of 5,10‐bis(pentafluorophenyl)tripyrrane with 3,5‐di‐tert‐butyl‐4‐hydroxybenzaldehyde. The reduction of 9 with NaBH₄ afforded the Möbius aromatic [28]hexaphyrin 10 . Bis‐rhodium complex 11 , prepared from the reaction of 10 with [{RhCl(CO)₂}₂], displays strong Hückel antiaromatic character because of the 28 π electrons that occupy the conjugated circuit on the enforced planar structure. The oxidation of 11 with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) yielded complexes 12 and 13 depending upon the reaction conditions. Both 12 and 13 are planar owing to bis‐rhodium metalation. Although complex 12 bears two meso‐OCH groups at the long sides and is quinonoidal and nonaromatic in nature, complex 13 bears 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl and OCH groups and exhibits a moderate diatropic ring current despite its cross‐conjugated electronic circuit. The diatropic ring current increases upon increasing the solvent polarity, most likely due to an increased contribution of an aromatic zwitterionic resonance hybrid.     

Selective Generation of Formamides through Photocatalytic CO2 Reduction Catalyzed by Ruthenium Carbonyl Compounds

The selective formation of dialkyl formamides through photochemical CO₂ reduction was developed as a means of utilizing CO₂ as a C₁ building block. Photochemical CO₂ reduction catalyzed by a [Ru(bpy)₂(CO)₂]²⁺ (bpy: 2,2′‐bipyridyl)/[Ru(bpy)₃]²⁺/Me₂NH/Me₂NH₂⁺ system in CH₃CN selectively produced dimethylformamide. In this process a ruthenium carbamoyl complex ([Ru(bpy)₂(CO)(CONMe₂)]⁺) formed by the nucleophilic attack of Me₂NH on [Ru(bpy)₂(CO)₂]²⁺ worked as the precursor to DMF. Thus Me₂NH acted as both the sacrificial electron donor and the substrate, while Me₂NH₂⁺ functioned as the proton source. Similar photochemical CO₂ reductions using R₂NH and R₂NH₂⁺ (R=Et, nPr, or nBu) also afforded the corresponding dialkyl formamides (R₂NCHO) together with HCOOH as a by‐product. The main product from the CO₂ reduction transitioned from R₂NCHO to HCOOH with increases in the alkyl chain length of the R₂NH. The selectivity between R₂NCHO and HCOOH was found to depend on the rate of [Ru(bpy)₂(CO)(CONR₂)]⁺ formation.