The effect of high hydrostatic pressure on taste substance distribution in fresh green tea leaves

ABSTRACT

High hydrostatic pressure (HHP) can be an alternative method to steaming to inhibit enzymatic fermentation in green tea making process. However, the effect of HHP treatment on green tea taste is not clear. Thus, this study aimed to determine the effect of HHP on substances associated with green tea taste. Fresh green tea leaves were immediately treated with HHP at 300, 500, or 700?MPa for 10, 30, or 60 min at 25°C. The concentration of free amino acids, catechins, and caffeine in HHP-treated samples was quantified by LC-MS. The taste intensity of the samples was detected by taste sensors. HHP resulted in a high accumulation of free amino acids in green tea leaves, which was likely due to proteolysis. In particular, theanine synthesis may have been promoted by an increase in the concentration of substrates during HHP. Compared to steaming, HHP enhanced umami richness, and inhibited bitterness and astringency.     

Hydrogen Production System by Light-Induced α-FeOOH Coupled with Photoreduction

Solar-driven catalysts on semiconductors to produce hydrogen are considered as a means to solve environmental issues. In this study, H₂ production coupling with oxygen consumption by noble metal-free α-FeOOH was demonstrated even though the conduction band edge was lower than the reduction potential of H⁺ to H₂. For activation of α-FeOOH, an electron donor, Hg-Xe irradiation, and low pH (ca. 5) were indispensable factors. The H₂ production from H₂O was confirmed by GC-MS using isotope-labeled water (D₂O) and deuterated methanol. The α-FeOOH synthesized by coprecipitation method showed 25 times more active than TiO₂. The photocatalytic activity was stable for over 400 h. Our study suggests that α-FeOOH known as rust can produce H₂ by light induction.     

Perylene-Cy3 FRET System to Analyze Photoactive DNA Structures

We report a new Förster resonance energy transfer (FRET) system for structural analyses of DNA duplexes using perylene and Cy3 as donor and acceptor, respectively, linked at the termini of a DNA duplex via D-threoninol. Experimentally obtained FRET efficiencies were in good agreement with theoretical values calculated based on canonical B-form DNA. Due to the relatively long Förster radius, this system can be used to analyze large DNA structures, and duplexes containing photo-reactive molecules can be analyzed since perylene can be excited with visible light. The system was used to analyze a DNA duplex containing stilbene, demonstrating that in the region of the stilbene cluster the duplex adopts a ladder-like structure rather than helical one. Upon photodimerization between stilbene residues, FRET efficiencies indicated the reaction does not disturb DNA duplex. This FRET system will be useful for analysis of photoreactions of nucleobases as well as a wide range of nucleic acid structures.     

Experimental Investigation on Turbulent Structure of Drag Reducing Channel Flow with Blowing Polymer Solution from the Wall

Turbulent drag reducing flow with blowing polymer solution from the channel wall was investigated experimentally using particle image velocimetry (PIV). Experiments were carried out with varying conditions of blowing polymer solution (e.g. weight concentration of polymer solution). Reynolds number based on the channel height and mean velocity was set to 20000 and 40000. When the polymer solution was blown from the channel wall, streamwise velocity fluctuation little increased, but wall-normal velocity fluctuation, Reynolds shear stress and correlation coefficient decreased significantly only near the blower wall. This behavior corresponds to the decrease of the ejection and sweep in the near-wall region observed by the investigation of instantaneous velocity map. On the contrary, this characteristic behavior was not observed at a position away from the blower wall (y/(H/2) > 0.4) and the scatter plot was almost the same as that of the water flow in this region. These results suggest that there are two regions in the drag reducing flow with blowing polymer solution from the wall; one is a non-Newtonian region which exists near the blower wall, and the other is a Newtonian region at a distance from the wall. The non-Newtonian region plays a key role in the drag reduction by the blowing polymer solution.     

Enhancement of artificial promoter activity by ultrasound-induced oxidative stress

We previously developed artificial promoters that were activated in response to X-ray irradiation. Sonication with 1.0 MHz ultrasound that causes intracellular oxidative stress was found to activate some of these promoters though to lesser degrees. The most sensitive one among these promoters showed intensity- and duration-dependent activations by sonication. In addition, its activation by sonication was attenuated when N-acetyl cysteine was present, suggesting the involvement of intracellular oxidative stress in the activation mechanism. Improved promoters for sensitivity to X-ray irradiation were also found more sensitive to sonication. The most improved one showed 6.0 fold enhancement after sonication with 1.0 MHz ultrasound at 1.0 W/cm² for 60 s. This enhancement was also attenuated with the presence of N-acetyl cysteine. When stably transfected HeLa cells with the most sensitive promoter were transplanted on to mice and sonicated, luciferase activity by the promoter increased to 1.35 fold in average though it was not statistically significant compared to control. Although gene regulation in vivo by sonication was not clear, this is the first report on artificially constructed promoters responsive to ultrasound.     

Total synthesis of (−)-amathaspiramide F

The stereoselective total synthesis of the marine alkaloid, (−)-amathaspiramide F (1), was achieved from the α-hydroxy-α-ethynylsilane 2. The key steps involved in the synthesis were (1) the enolate Claisen rearrangement of the α-acyloxy-α-alkenylsilane for the stereoselective construction of the consecutive C5 and C9 chiral centers of 1 (erythro configuration), (2) the construction of aza-spirohemiaminal 28, and (3) dibromination during the final stage of the total synthesis. The reaction of the (Z)-α-acyloxy-α-alkenylsilane 22 possessing the Boc-homoallylglycine ester as the acyloxy group underwent stereoselective enolate Claisen rearrangement to give the desired erythro product 23. On the other hand, the reaction of the α-acyloxy-α-alkenylsilane (Z)-5 having Boc-proline gave the unexpected threo product 6. Oxidative cleavage of the vinylsilane group of 23 followed by treatment with heptamethyldisilazane as the methylamine equivalent gave aza-spirohemiaminal 28. The problematic regioselective dibromination to 28 was achieved using n-Bu₄NBrCl₂.     

The Turaev genus of an adequate knot

The Turaev genus of a knot is an obstruction to the knot being alternating. An adequate knot is a generalization of an alternating knot. A natural problem is a characterization of the Turaev genus of an adequate knot. In this paper, we show that the Turaev genus of an adequate knot is realized by the genus of the Turaev surface associated to an adequate diagram of the knot using the Khovanov homology. As a result, we obtain the additivity of the Turaev genus of adequate knots, and show that the Turaev genus of an adequate knot is “often” preserved under mutation. We also show that an n-semi-alternating knot is of Turaev genus n. This is the first examples of adequate knots of Turaev genus two or more.     

Direct Observation of Trapped Gas Bubbles by Capillarity in Sandy Porous Media

We investigated the mechanism of residual gas trapping at a microscopic level. We imaged trapped air bubbles in a Berea sandstone chip after spontaneous imbibition at atmospheric pressure. The pore structure and trapped bubbles were observed by microfocused X-ray computed tomography. Distributions of trapped bubbles in Berea and Tako sandstone were imaged in coreflooding at a capillary number of 1.0 × 10⁻⁶. Trapped bubbles are of two types, those occupying the center of the pore with a pore-scale size and others having a pore-network scale size. In low-porosity media such as sandstone, connected bubbles contribute greatly to trapped gas saturation. Effects of capillary number and injected water volume were investigated using a packed bed of glass beads 600μm in diameter, which had high porosity (38%). The trapped N₂ bubbles are stable against the water flow rate corresponding to a capillary number of 1.0 × 10⁻⁴.     

Mg5TiO4(BO3)2

Single crystals of pentamagnesium titanium(IV) tetraoxide bis(borate), Mg₅TiO₄(BO₃)₂, were prepared by slow cooling of the melt from 1623 K in air. The crystal is isostructural with the mineral ludwigite (Mg₂FeO₂BO₃). The Mg and Ti atoms are coordinated by six O atoms and the B atom is coordinated by three O atoms. There are three Mg sites and one mixed site statistically occupied by Mg and Ti atoms. Atoms are at the following special positions: 2a (0, 0, 0) and 2d (0, , ) for two Mg atoms, 4g (x, y, 0) for the mixed Ti/Mg site and the BO₃ group, and 4h (x, y, ) for a third Mg and two oxide O atoms. MgO₆ and (Ti/Mg)O₆ octahedra are connected by sharing of edges to form zigzag folding layers along the c axis. Triangular prismatic tunnels are formed between the folding layers by sharing apical O atoms of the MgO₆ and (Ti/Mg)O₆ octahedra.     

Convenient preparation of 4-arylmethyl- and 4-hetarylmethyl thiazoles by regioselective cycloaddition reactions of 3-sulfanyl- and selanylpropargyl alcohols

Complete details of thiazole syntheses by scandium-catalyzed cycloaddition reactions of 1-aryl- and 1,1-bisaryl-3-phenylsulfanylpropargyl alcohols with thioamides are described. Reactions of 1,1-bisarylpropargyl alcohols with thioamides and selenamide in MeNO₂/H₂O resulted in 4-bisarylmethyl-1,3-thiazoles 4aa-ic and 4H-4,4-bisaryl-1,3-thiazines 5ea-ga in high yields. Reactions in MeNO₂/D₂O resulted in 4-bisaryldeuteriomethyl-1,3-thiazoles 10ca-ia with high deuterium purity. Reactions of dialkyl and alkyl aryl propargyl alcohols are also described.