Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3]

The triangular six-electron cluster complex [Mo₃S₄Cl₄(PEt₃) _x (thf)₅] produced by the excision reaction of Mo₃S₇Cl₄ with triethypholsphine is reduced by magnesium at – 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo₃S₄Cl₃(dppe)₂(PEt₃)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5) = 121.73(2)°,V = 3858(2) A³, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.Dedicated to Professor fiaxi Lu on the occasion of his 80th birthday.     

Effect of divalent cations on the volume of a maleic acid copolymer gel examined by incorporating lysozyme

An ionic gel of poly(maleic acid-alt-methyl vinyl ether) cross-linked by 1,6-hexanediol was prepared with molar ratio of 1/0.5 at 50 °C. The gels with different molar ratios at different temperatures were also prepared for comparison. Their swelling-shrinkage profiles were examined by measuring the ratio of initial to final weights at various pHs and CaCl₂ concentrations in buffer solution. The gel squeezed remarkably in the presence of Ca²⁺ for pH>6.3, corresponding to the solution properties of maleic acid copolymer. No appreciable change was observed below pH 6.3. To estimate free space in the gel in more detail, lysozyme was incorporated into the free space, and its release rate was measured under several CaCl₂ concentrations. The time course of the release was either simple or complicated, depending on pH and CaCl₂ concentration. The control mechanism of the release of lysozyme from the gel network may be widely applicable to the drug delivery system.     

Analysis of small amounts of solid samples by spark-source mass spectrometry

Various elements were determined in solid samples weighing < 2 mg by spark-source mass spectrometry. The samples were fixed on the top of a cylindrical graphite electrode using a conductive silver paint. After baking, the samples were sparked against a tantalum or gold wire. The method was used for the determination of impurities in steel, iron, molybdenum and CdSe. For samples weighing ca. 1 mg, detection limits of the order of 1 μg g^?1 were obtained. A relationship between the relative sensitivity factor and physical properties is proposed.     

Immobilization of individual cells by local photo-polymerization on a chip

A novel separation method for random screening of target cells from a large heterogeneous population by using a local photo-polymerization is developed. A photo-crosslinkable resin solution is mixed with the sample liquid and we controlled the state from sol to gel by irradiating the near ultraviolet (UV) light with the mercury lamp and He-Cd laser near the target cell. We applied three types of immobilization methods such as direct immobilization method, caging method, and direct immobilization with position control method. The selected cell is immobilized in the cured resin directly or inside the cage of the cured resin. In the position control method, laser tweezers are employed to manipulate the target cell indirectly by using the droplet of the resin as a microtool. The cell is positioned properly by the laser manipulation system and is immobilized in the polymerized resin. After the selected cells are immobilized we can easily remove the other objects by the cleaning flow in the microchannel since the polymerized resin strongly binds with the cover glass and resists more than 466 mm s(-1) flow speed in the microchannel (microchannel size: width is 500 micron and depth is 100 micron). We tested the mercury lamp as well as the He-Cd laser for UV-light irradiation at the local area and confirmed improvement of resolution of the cured area by using the He-Cd laser (from 7 micron to 5 micron). Based on this method, we succeeded in single cell immobilization and basic experiments such as culture and fluorescent dyeing of immobilized yeast cells.     

Stereoselective synthesis of cis and trans-fused 3a-aryloctahydroindoles using cyclization of N-vinylic α-(methylthio)acetamides: synthesis of (−)-mesembrane

Treatment of N-(2-arylcyclohex-1-en-1-yl)-α-(methylthio)acetamides with N-chlorosuccinimide (NCS) gave 3a-aryl-2,3,3a,4,5,6-hexahydro-3-(methylthio)indol-2-ones. Desulfurization of the cyclization products followed by a catalytic hydrogenation of the resulting hexahydroindol-2-ones gave predominantly or exclusively trans-fused octahydroindol-2-ones. On the other hand, reduction of the desulfurization products with Et₃SiH in CF₃CO₂H exclusively provided cis-fused octahydroindol-2-ones. A chiral induction of N-[2-(3,4-dimethoxy)phenylcyclohex-1-en-1-yl]-α-(methylthio)acetamide having an (R)-1-(1-naphthyl)ethyl group on the nitrogen atom led to the synthesis of (−)-mesembrane and (−)-trans-mesembrane.     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. I. p-isopropenylphenyl glycidyl ether: An epoxy-functionalized α-methylstyrene

p-Isopropenylphenyl glycidyl ether (IPGE), a monomer of dual cationic functionality (isopropenyl and epoxy), was polymerized by a variety of initiators, and optimum conditions were established for its selective vinyl cationic polymerization. The hydrogen iodide/iodine (HI/I₂) initiating system or iodine polymerized selectively the isopropenyl group in CH₂Cl₂ at a low temperature (?78°C), to produce soluble poly(IPGE) with epoxy pendants. Under these conditions, the number-average molecular weight of the polymers was inversely proportional to the initial initiator concentration, indicating the formation of long-lived propagating species. Soluble poly(IPGE) was also obtained at ?15 and ?40°C by HI/I₂ or iodine. However, at these higher temperatures, transfer and/or termination reactions took place to give olefin-terminated polymers, in which some of the pendant epoxy groups were consumed. BF₃OEt₂ (a metal halide) and CF₃SO₃H (a strong protonic acid) polymerized both epoxy and isopropenyl groups of IPGE and yielded crosslinked insoluble polymers.     

INACTIVATION ACTION SPECTRA OF BACILLUS SUBTILIS SPORES IN EXTENDED ULTRAVIOLET WAVELENGTHS (50–300nm) OBTAINED WITH SYNCHROTRON RADIATION

Five types of Bacillus subtilis spores (UVR, UVS, UVP, RCE, and RCF) differing in repair and/or recombinational capabilities were exposed to monochromatic radiations at 13 wavelengths from 50 to 300 nm in vacuum. An improved biological irradiation system connected to a synchrotron radiation source was used to produce monochromatic UV radiation in this extended wavelength range with sufficient fluence to inactivate bacterial spores. From the survival curves obtained, the action spectra for the inactivation of the spores were depicted. Recombination-deficient RCE (recE) and RCF (recF) spores were more sensitive than the wild-type UVR spores in the entire range of wavelengths. This was considered to mean that DNA was the major target for the inactivation of the spores. Vacuum-UV radiations of 125-175 nm were effective in killing the spores, and distinct peaks of the sensitivity were seen with all types of the spores. Insensitivities at 190 and 100 nm were common to all five types of spores, indicating that these wavelengths were particularly impenetrant and absorbed by the outer layer materials. The vacuum-UV peaks centering at 150 nm were prominent in the spores defective in recombinational repair, while the far-UV peaks at around 235 and 270 nm were prominent in the UVS (uvrA ssp) and UVP (uvrA ssp polA) spores deficient in removal mechanisms of spore photoproducts. Thus, the profiles of the action spectra were explained by three factors; the penetration depth of each radiation in a spore, the efficiency of producing DNA damage that could cause inactivation, and the repair capacity of each type of spore.     

Effects of preparing and ligand-binding methods of small unilamellar liposomes on their blood elimination and tissue distribution in rats

The effects of two methods of preparing small unilamellar vesicles (SUV) (detergent removal or sonication) on their in vivo elimination and tissue distribution was investigated in rats. The SUV prepared by either method had the same size distribution and lipid composition (egg yolk phosphatidylcholine/cholesterol/dipalmitoyl phosphatidylethanolamine or palmitic acid = 20/10/0.3, molar ratio). Three types of SUV made by either method were prepared. These contained one of three different surface ligand-binding functional groups (N-hydroxysuccinimide ester of palmitic acid, NHSP; glutaraldehyde-phosphatidylethanolamine, GA-PE; N-[4-(p-maleimidophenyl)butyryl]phosphatidylethanolamine, MPB-PE). SUV prepared by detergent removal were eliminated slowly from the circulation, and exhibited a low liver uptake and little leakage of [3H]inulin. There was no significant difference in elimination of the NHSP-SUV, GA-SUV or MPB-SUV prepared by detergent removal and their tissue distribution was similar. In contrast, the sonicated SUV were eliminated from the circulation much more rapidly mainly by liver uptake. The leakage of [3H]inulin from sonicated SUV into urine was relatively large. When sonicated control-SUV were prepared in the presence of the antioxidant, alpha-tocopherol (alpha-T-SUV), which reduces lipid peroxidation during sonication, the alpha-T-SUV were eliminated slowly with only a low liver uptake. Our results indicate that the rapid elimination and greater liver uptake of sonicated SUV is partly due to lipid peroxidation during preparation. These findings have relevance to the use of liposomes as a drug delivery system.     

Polymerization of tert-alkylacetylenes by Mo- and W-based catalysts

Polymerization of three tert-alkylacetylenes (3,3-dimethyl-1-pentyne, 3,3-dimethyl-1-nonyne, 1-adamantylacetylene) by Mo- and W-based catalysts provided new polymers in virtually quantitative yields. In contrast, Ziegler catalysts did not polymerize these monomers. Every polymer had a form of white solid, and had alternating double bonds along the main chain. Though some of poly(3,3-dimethyl-1-pentyne)s contained a toluene-insoluble fraction, the polymer was totally soluble when proper polymerization conditions were chosen. The molecular weights of soluble fractions were as high as 3 × 10⁵. Poly(3,3-dimethyl-1-nonyne) was also partly insoluble in toluene, and the quantity of soluble fraction was less than that of poly(3,3-dimethyl-1-pentyne). The geometric structure of these two polymers could be controlled by the choice of suitable polymerization conditions. Poly(1-adamantylacetylene) was insoluble in any organic solvents. Copolymerization of 1-adamantylacetylene with suitable comonomers afforded soluble copolymers.     

Coupling reaction of poly(α-methylstyryl) anion with (MMA–α-methylstyrene) block copolymer

(MMA–α-methylstyrene)block copolymer was reacted with poly(α-methylstyryl)anion at ?78°C in a mixture of good tetrahydrofuran (THF) and poor methylcyclohexane solvents. The reaction conditions were chosen so as to produce graft copolymers made up of a backbone (AB-type block copolymer) and a single branched chain (1:2 graft copolymer). Gel permeation chromatograph (GPC), osmotic pressure measurement, and elemental analysis were used for the characterization of 1:2 graft copolymer. It appeared that poly(α-methylstyryl)anion reacted with the end pendant groups located farthest away from the branched point of AB-type block copolymer, when the dimensions of AB-type block copolymer molecule are small.