High pressure Raman study on the local structure of 1-ethyl-3-methylimidazolium tetrafluoroborate

We have investigated the pressure-induced Raman spectral changes of 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF₄]). We found that [emim][BF₄] did not crystallize up to 1.2 GPa. The Raman CH stretching spectra arising from the CH₃ groups of the ethyl-chain and the CH₃ group adjacent to the imidazolium-ring in [emim]⁺ cation largely changed against pressure. Moreover, the Raman intensity of the CH₂ (N) bending band arising from the alkyl-chain drastically changes with increasing pressure, but that of the imidazolium-ring in-plane bending band arising from the imidazolium-ring is independent of pressure. Our results show that the environment around the alkyl-chain of [emim][BF₄] is largely perturbed rather than that around the imidazolium-ring upon compression.     

Tensor analyzing power T 20 of the dd → 3Hen and dd → 3Hp reactions at zero angle for energies 140, 200, and 270 MeV

RIKEN Accelerator Research Facility data on the tensor analyzing power T ₂₀ of the dd → ³Hen and dd → ³Hp reactions at zero angle for deuteron kinetic energies of 140, 200, and 270 MeV are reported. The observed positive sign of T ₂₀ clearly demonstrates the sensitivity to the D/S-wave ratio in the ³He and ³H wave functions in the energy range of the experiment. Data on T ₂₀ for the ³Hen channel are in agreement with those for the ³Hp channel within the experimental errors.     

Measurement of Flexo-coefficients for Nematic LCs without the Influence of the Impurity Ions by Using the Chromatographic Isolation Method

The sum of the flexo-coefficients (e₁₁+e₃₃) was measured by the capacitance characteristic depending on the applied dc voltage in the HAN cell. The voltage for the minimum value of the capacitance was shifted by the influence of flexoelectric effect. One of the important problems for the evaluation for the flexo effect was the influence of impurity ions. Then, the chromatographic isolation phenomenon was used to separate impurity ions when the LC material was injected into the empty cell by the capillary action. The coefficient (e₁₁+e₃₃) of ZLI-4792 was measured, and a value of 26.0 pC/m was obtained.     

FT-NIR Spectroscopy of some long-chain fatty acids and alcohols

Fourier-transform (FT) near-infrared (NIR) spectroscopy has proved to be a powerful technique in investigating structure and thermodynamic properties of long-chain fatty acids and alcohols. In order to extract useful information from the NIR spectra, bands due to the second as well as first overtones of OH-stretching modes of the monomeric forms were employed. It has been also found that two-dimensional (2D) NIR correlation spectroscopy can accentuate useful information often obscured in the complicated NIR spectral data set.     

Biosynthesis of Indole Diterpene Lolitrems: Radical-Induced Cyclization of an Epoxyalcohol Affording a Characteristic Lolitremane Skeleton

Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome-editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical-induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue.     

Signal-to-noise ratio improvement by stochastic resonance in moments in non-dynamical systems with multiple states

Conventional stochastic resonance in terms of signal-to-noise ratio refers to the amplification of a weak signal in the average of the output. In this framework, only the first moment of the output is used for extracting the information about the input signal. However, higher order moments are also modulated by the input signal. We report the occurrence of stochastic resonance in higher moments. Furthermore, by the linear combination of moments, the signal-to-noise ratio improves compared with the conventional method, which uses the lowest moment only.     

Synthesis of Nano‐Sized TiO2 Colloidal Sol and Its Optical Properties

Nano‐sized TiO₂ sol was prepared through a wet synthesis process. The synthesis procedure involved hydrolysis of TiCl₄, acid treatment, and a SiO₂ surface‐modifying process. Before surface modification, the TiO₂ suspension was treated with acid to remove Na ions, soluble TiO_2, and other impurities. The acid treatment of a TiO₂ suspension at a higher temperature was proved to be useful for effective SiO₂ modification. The colloidal sol provided high transparency in visible light as well as excellent UV‐shielding properties. Surface modification of TiO₂ particles with SiO₂ greatly improved both the dispersing stability in neutral pH and the photostability of TiO₂ colloidal sol.     

Molecular origin for rheological characteristics of native gellan gum

The ¹H-nuclear magnetic resonance spectrum showed that the l-rhamnosyl residues of native gellan gum were coinvolved in both a small number of ⁴C₁-pyranose conformations and a large number of ¹C₄-pyranose conformations, whereas for deacylated polymer, almost of the residues were involved in ⁴C₁-pyranose conformation. The flow curves of native gellan gum showed plastic behavior above 0.2%. The elastic modulus stayed at a constant value with increase in temperature up to 40 °C, then decreased rapidly. The elastic modulus increased with addition of CaCl₂ (6.8 mM) and stayed constant value with increase in temperature up to 65 °C, then decreased rapidly. The stronger elastic modulus was observed in deacylated gellan gum with addition of CaCl₂. The elastic modulus of native gellan gum showed larger value than that in aqueous solution in the presence of urea (4.0 M). Intra- and intermolecular associations of native gellan gum molecules in the presence of Ca⁺² were proposed.     

Total synthesis of polygalolide A

The total synthesis of polygalolide A was accomplished through intramolecular C-glycosylation of glucal modified with siloxyfuran. The siloxyfuran group and siloxy substituent at the C-3 position played crucial roles in allowing direct access to the highly substituted oxabicyclo[3.2.1] core skeleton with correct quaternary stereogenic centers.     

Disruption of reverse micelles and release of trapped ribonuclease A photochemically induced by Malachite Green leuconitrile derivative

Photoinduced disruption of a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle is triggered by a Malachite Green leuconitrile derivative (MGL). UV irradiation of MGL solubilized in an AOT-water-chloroform mixture creates a cationic surfactant that interacts electrostatically with the anionic AOT. We investigated the disruption of the reverse micelle by using proton nuclear magnetic resonance spectroscopy and found that UV irradiation of MGL decreases the number of water molecules solubilized in the interior of the AOT reverse micelles. Furthermore, the photoinduced disruption of the reverse micelle is shown to release ribonuclease A, which is trapped in the water in the interior of the AOT reverse micelle. This photoinduced release may offer a desirable transport system of biopolymers.