Electronic nature of substituent X governs reaction mechanism in aminolysis of 4-pyridyl X-substituted-benzoates in acetonitrile

A kinetic study is reported for aminolysis of 4-pyridyl X-substituted-benzoates 5a-i. Plots of pseudo-first-order rate constants (k(obsd)) vs [amine] curve upward for the reactions of substrates possessing a strong electron-withdrawing group in the benzoyl moiety (5a-d) but are linear for the reactions of those bearing an electron-donating group (5e-i), indicating that the electronic nature of substituent X governs the reaction mechanism. The k(1)k(2)/k(-1) and k(1)k(3)/k(-1) values were calculated from the intercept and slope of the linear plots of k(obsd)/[amine] vs [amine], respectively. The Hammett plot for k(1)k(2)/k(-1) consists of two intersecting straight lines, while the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρ(X) = 0.41 and r = 1.58, implying that the nonlinear Hammett plot is not due to a change in rate-determining step but is caused by stabilization of substrates possessing an electron-donating group through resonance interactions. The small ρ(X) suggests that the k(2)/k(-1) ratio is little influenced by the nature of substituent X. The Br?nsted-type plots for aminolysis of 4-pyridyl 3,5-dinitrobenzoate 5a are linear with β(nuc) = 0.98 and 0.79 for k(1)k(2)/k(-1) and k(1)k(3)/k(-1), respectively. The effect of amine basicity on the microscopic rate constants is also discussed.     

Effect of Pretreatment Severity on Accumulation of Major Degradation Products from Dilute Acid Pretreated Corn Stover and Subsequent Inhibition of Enzymatic Hydrolysis of Cellulose

The concept of reaction severity, which combines residence time and temperature, is often used in the pulp and paper and biorefining industries. The influence of corn stover pretreatment severity on yield of sugar and major degradation products and subsequent effects on enzymatic cellulose hydrolysis was investigated. The pretreatment residence time and temperature, combined into the severity factor (Log R _o), were varied with constant acid concentration. With increasing severity, increasing concentrations of furfural and 5-hydroxymethylfurfural (5-HMF) coincided with decreasing yields of oligosaccharides. With further increase in severity factor, the concentrations of furans decreased, while the formation of formic acid and lactic acid increased. For example, from severity 3.87 to 4.32, xylose decreased from 6.39 to 5.26?mg/mL, while furfural increased from 1.04 to 1.33?mg/mL; as the severity was further increased to 4.42, furfural diminished to 1.23?mg/mL as formate rose from 0.62 to 1.83?mg/mL. The effects of dilute acid hydrolyzate, acetic acid, and lignin, in particular, on enzymatic hydrolysis were investigated with a rapid microassay method. The microplate method gave considerable time and cost savings compared to the traditional assay protocol, and it is applicable to a broad range of lignocellulosic substrates.     

Electro-Optical Properties of Electric Field-Induced-Polymer Stabilization at Blue Phase of Chiral Nematic Liquid Crystal

Polymer stabilization of the blue phase induced a wide temperature range of more than 60 K, but the high driving voltage and the large switching hysteresis compared to the low molecular weight blue phase of the chiral nematic liquid crystal. In this study, we newly proposed electric field-induced-polymer stabilization of blue phase (EFIPSBP) which the electric field was applied to the blue phase during polymer stabilization and investigated the driving voltage and the switching hysteresis using various voltage-applied EFIPSBP cells. We confirmed that the driving voltage and the switching hysteresis of the EFIPSBP cell were decreased compared to those of conventional polymer stabilized BP at 8OCB chiral nematic liquid crystal mixture. This could be suggested as a potential method for improving the driving voltage and the switching hysteresis of conventional polymer stabilized BP.     

Pitfalls in assessing the α-effect: reactions of substituted phenyl methanesulfonates with HOO(-), OH(-), and substituted phenoxides in H(2)O

Toward resolving the current controversy regarding the validity of the α-effect, we have examined the reactions of Y-substituted phenyl methanesulfonates 1a-1l with HOO(-), OH(-), and Z-substituted phenoxides in the gas phase versus solution (H(2)O). Criteria examined in this work are the following: (1) Br?nsted-type and Hammett plots for reactions with HOO(-)and OH(-), (2) comparison of β(lg) values reported previously for the reactions of Y-substituted phenyl benzenesulfonates 2a-2k with HOO(-) (β(lg) = -0.73) and OH(-) (β(lg) = -0.55), and for those of 1a-1l with HOO(-) (β(lg) = -0.69) and OH(-) (β(lg) = -1.35), and (3) Br?nsted-type plot showing extreme deviation of OH(-) for reactions of 2,4-dintrophenyl methanesulfonate 1a with aryloxides, HOO(-), and OH(-), signifying extreme solvation vs different mechanisms. The results reveal significant pitfalls in assessing the validity of current interpretations of the α-effect. The extreme negative deviation by OH(-) must be due, in part, to the difference in their reaction mechanisms. Thus, the apparent dependence of the α-effect on leaving-group basicity found in this study has no significant meaning due to the difference in operating mechanisms. The current results argue in favor of a further criterion, i.e., a consistency in mechanism for the α-nucleophiles and normal nucleophiles.     

Mesh-integrated microdroplet array for simultaneous merging and storage of single-cell droplets

We constructed a mesh-grid integrated microwell array which enables easy trapping and consistent addition of droplets. The grid acts as a microchannel structure to guide droplets into the microwells underneath, and also provides open access for additional manipulation in a high-throughput manner. Each droplet in the array forms a stable environment of pico-litre volume to implement a single-cell-based assay.     

Observation of methanol behavior in fuel cells in situ by NMR spectroscopy

The chemical conversion of methanol in direct methanol fuel cells was followed in situ by NMR spectroscopy. Comparing data of the methanol oxidation on Pt and PtRu anode catalysts allowed the role of Ru in both Faradaic and non-Faradaic reactions to be investigated. The spatial distributions of chemicals could also be determined. (Picture: T1-T4=inlet and outlet tubes.).     

Oleuropein prevents the progression of steatohepatitis to hepatic fibrosis induced by a high-fat diet in mice

Nonalcoholic steatohepatitis (NASH) is characterized by hepatocyte injury and inflammatory cell infiltration, which has been linked to peripheral insulin resistance and increased levels of triglycerides in the liver. The purposes of this study were to establish a mouse model of NASH by feeding mice a 60% high-fat diet (HFD) and to demonstrate the anti-fibrotic effects of oleuropein, which has been shown to have anti-oxidant and anti-inflammatory properties, in this HFD-induced mouse model of NASH. C57BL/6 mice were divided into three groups: a regular diet group (Chow), a HFD group and an oleuropein-supplemented HFD group (OSD), which was fed a 0.05% OSD for 6 months. The effects of oleuropein in this model were evaluated using biochemical, histological and molecular markers. The expression levels of alpha-smooth muscle actin (α-SMA)and collagen type I in the HFD and OSD groups were evaluated using real-time PCR and western blotting. The body weight, biochemical marker levels, nonalcoholic fatty liver disease activity score, homeostasis model of assessment-insulin resistance (HOMA-IR) and leptin levels observed in the HFD group at 9 and 12 months were higher than those observed in the Chow group. The HOMA-IR and leptin levels in the OSD group were decreased compared with the HFD group. In addition, α-SMA and collagen type I expression were decreased by oleuropein treatment. We established a NASH model induced by HFD and demonstrated that this model exhibits the histopathological features of NASH progressing to fibrosis. Our results suggest that oleuropein may be pharmacologically useful in preventing the progression of steatohepatitis and fibrosis and may be a promising agent for the treatment of NASH in humans.     

Synthesis and Characterization of New Dibenzothiophene-based Host Materials for Blue Phosphorescent Organic Light-Emitting Diodes

A series of bipolar host materials containing dibenzo[b,d]thiophene (DBT) or dibenzo[b,d]thiophene 5,5-dioxide core were successfully synthesized, and their physical, photophysical, and electrochemical properties were investigated. The three host materials showed well-localized electron distribution at the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states, as evidenced by theoretical calculations. Triplet energies of the new host materials are higher than 2.6 eV, and the blend film with bis[2-(4,6-difluorophenyl)pyridinato-C² Misra, A. et al. (2006). Semicond. Sci. Technol., 21, R35.[Crossref], [Web of Science ®] , [Google Scholar],N](picolinato)iridium(III) (FIrpic) as a blue phosphorescent dopant showed highly efficient energy transfer between the host material and dopant.