Ammonia sensor with flavin-containing monooxygenase

A biosensor for ammonia solution was developed with a flavin-containing monooxygenase-3 (FMO3). The biosensor consisted of a Clark-type dissolved oxygen electrode and an FMO3 immobilized membrane. In order to amplify the biosensor output, a substrate regeneration cycle obtained by coupling the monooxygenase with L-ascorbic acid (AsA) as the reducing reagent system, was applied. The AsA 10.0?mmol?L^?1 concentration was able to optimally amplify the sensor output 11 times greater. The FMO3 biosensor was used with AsA to measure ammonia solution from 3.20 to 14.29?mmol?L^?1 and from 0.09 to 21.7?mmol?L^?1 with 5.0 and 10.0?mmol?L^?1 AsA, respectively. The FMO biosensor also had a good reproducibility such as a 2.5% coefficient of variation in eight multiple measurements, and the output current was maintained over a few hours. The selectivity of the FMO biosensor being attributed to enzyme specificity was obtained for several chemical substances (trimethyl amine, methyl mercaptan, dimethyl sulphide, and so on).     

Synthetic Approach Toward Antibiotic Tunicamycins, 4. X-Ray Crystal Structure Analysis of a Higher-Carbon Nitro Sugar

Abstract

A higher-carbon carbohydrate, a derivative of undecose has been synthesized by the potassium fluoride-catalyzed addition of a nitro sugar to a sugar aldehyde. The addition of methyl 5-de-oxy-2,3-O-isopropylidene-5-nitro-β-D-ribofuranoside to methyl 2-benzyloxycarbonylamino-2-deoxy-3,4-O-isopropylidene-α-D-galacto-dialdopyranoside-(1, 5) yielded a single diastereomer of the nitro undecose derivative. The absolute configuration of two chiral centers of the derivative has been established by the X-ray crystal structure analysis.     

Hydrindacene‐Based Acetylenic Macrocycles with Horizontally and Vertically Ordered Functionality Arrays

The macrocyclization of 2,6‐diethynyl hydrindacenes ( 1 ) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle ( 2 ) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle ( 3 ) demonstrates a moderate degree of geometrical flexibility as a result of the five‐membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π‐conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups.     

Molecular Flow and Lanthanum -Catalyzed Bond Interchange in Sodium Phosphate Polymers

Abstract

It is observed that sodium phosphate polymers, in which some of the Na⁺ ions have been replaced by La³⁺ ions, are subject to both simple molecular flow and to bond interchange in the glass transition region. These two relaxation mechanisms are separated, and their relative contributions to the shear viscosity are calculated. It is shown that the bond-interchange mechanism is subject to an activation energy of ca. 50 kcal, while that of the molecular flow is of the order of 200 kcal at Tg + 30°C;the latter is of the WLF form. It is further shown that the La³⁺ ions act as cross-links, at least at low concentrations, and that bond interchange occurs at the site of the La³⁺ ions rather than at random along the polymer chain.     

Control of Microphase Separation of Polystyrene-Silica Nanocomposites by Using Perhydropolysilazane and Partially Epoxidized Poly(styrene-block-butadiene-block-styrene)

In order to control microphase separation of polystyrene-silica nanocomposites, perhydropolysilazane (PHPS), which is a preceramic of silica, and epoxidized poly(styrene-block-butadiene-block-styrene) triblock copolymer [E-SBS, M_w = 8.0 × 10⁴, styrene: 40 mol%, degree of epoxidization of butadiene: 20 mol%] or poly(styrene-block-butadiene-block-styrene) triblock copolymer [SBS, M_w = 1.40 × 10⁵, styrene: 30 mol%] as templates of microphase separation were blended, following the calcination of composites in steam at 60°C. Well-arranged microphase separation was formed with E-SBS, though the macrophase separation was formed with SBS. The morphology of the microphase separation of the composites with E-SBS and PHPS was widely controlled by varying the PHPS content based on Molau's law. Silica domains were formed in polybutadiene domains. NMR analysis indicated the interaction between silanyl group of PHPS and epoxy group in E-SBS. The composites on the substrate were highly transparent and the surface of the composite with 73.5 vol% of silica was harder than 4H.     

SIMPLE METHOD FOR THE SYNTHESIS OF STANNOLE DIANION

Reduction of 1-t-butyl-1,2,3,4,5-pentaphenylstannole by lithium gave the stannole dianion. Reduction of the bi(1,1-stannole) having a t-butyl group on the tin by lithium also gave the stannole dianion, the formation of which was evidenced by spectral analysis and chemical trapping reaction.     

Degradation of TEMPO-oxidized cellulose fibers and nanofibrils by crude cellulase

The biodegradation behavior of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose fibers (TOCs) suspended in water and TEMPO-oxidized cellulose nanofibrils (TOCNs) dispersed in water by a commercial crude cellulase was studied. Products crude cellulase-treated for 0–7 days were separated into water/ethanol-insoluble and -soluble fractions. Weight recovery ratios and viscosity-average degrees of polymerization of the water/ethanol-insoluble fractions clearly decreased with crude cellulase-treatment time, showing that both TOCs and TOCNs have biodegradability. Water/ethanol-soluble fractions were subjected to size-exclusion chromatography (SEC) with photodiode array (PDA) detection to obtain SEC elution patterns detected by reflective index and UV spectra of each SEC pattern elution slice. SEC–PDA and ¹³C-NMR analyses showed that glucuronosyl unit-containing molecules present on microfibril surfaces in TOCs and TOCNs were primarily cleaved by hydrolyzing enzymes present as contaminants in the crude cellulase to form glucuronic acid as one of the major water-soluble degradation compounds. After the glucuronosyl units in TOCs and TOCNs were degraded and removed from microfibril surfaces by the hydrolyzing enzymes, cellulose chains newly exposed on the microfibril surfaces were rapidly hydrolyzed by cellulases predominantly present in the crude cellulase to form cellobiose. Both TOCs and TOCNs having sodium carboxyl groups are thus biodegradable, but TOCN having free carboxyl groups had clearly low biodegradability by the crude cellulase. Thus, biodegradation behavior may be controllable by controlling the structure of carboxyl group counter ions in TOCs and TOCNs.     

Iα → Iβ transition of cellulose under ultrasonic radiation

Aqueous suspensions of dispersed Glaucocystis cellulose microfibrils were sonicated at 4 °C for 3 h, using 24 kHz ultrasonic waves. This treatment induced a variety of ultrastructural defects, as the microfibrils became not only shortened, but also presented substantial damage materialized by kinks and subfibrillation. Upon analysis by X-ray diffraction and ¹³C solid-state NMR spectroscopy, it was found that the initial sample that contained 90 % of cellulose I_α allomorph became, to a large extent, unexpectedly converted into the I_β phase, while the loss of crystallinity was only moderate during the sonication treatment.     

Reaction of an “Invisible” Frustrated N/B Lewis Pair with Dihydrogen

D ‐(+)‐Camphor forms the enamine 2 with piperidine. Compound 2 adds HB(C₆F₅)₂ at the enamine carbon atom C3 to form a Lewis acid/Lewis base adduct (exo‐/endo‐isomers of 3 ). Exposure of 3 to dihydrogen (2.5 bar, room temperature) leads to heterolytic splitting of H₂ to form the H⁺/H^? addition products ( 4 , two diastereoisomers) of the “invisible” frustrated Lewis pairs ( 5 , two diastereoisomers) that were apparently generated in situ by enamine hydroboration under equilibrium conditions.     

Structure,Optical, and Magnetic Properties of (PPN+)2(C702−)⋅2 C6H4Cl2, which Contains Dianionic Polymeric (C702−)n Chains

A new salt, (PPN⁺)₂(C₇₀^2?) ? 2 C₆H₄Cl₂ ( 1 ), which contains C₇₀^2? dianions, has been obtained as single crystals (PPN⁺=bis(triphenylphosphine)iminium cation). The C₇₀^2? dianions form polymeric zigzag (C₇₀^2?)_n chains, in which the fullerene units are bonded through single C? C bonds of length 1.581(5)–1.586(6) Å. The distance between the centers of neighboring C₇₀^2? units is 10.441 Å. The optical and magnetic properties of (C₇₀^2?)_n have also been studied. Decreasing the symmetry of C₇₀ in the polymer activate about 20 new IR bands in addition to the 10 IR‐active bands of the starting C₇₀. The polymeric structure shows absorptions in the visible and NIR regions, with three main bands at 890, 1200, and 1550 nm, instead of one band of isolated C₇₀^2? dianions at 1165–1184 nm. We concluded that the (C₇₀^2?)_n polymer was diamagnetic, with a negative molar magnetic susceptibility of ?3.82×10^?4 emu mol^?1 per C₇₀^2? dianion. The polymer is EPR silent and a weak narrow EPR signal in salt 1 is due to impurities, which only constitute 0.84 % of spin S=1/2 of the total amount of fullerene C₇₀.