Cloning and functional characterization of a fructan 1-exohydrolase (1-FEH) in edible burdock (<Emphasis Type="Italic">Arctium lappa</Emphasis>L.)

Background  

We have previously reported on the variation of total fructooligosaccharides (FOS), total inulooligosaccharides (IOS) and inulin in the roots of burdock stored at different temperatures. During storage at 0°C, an increase of FOS as a result of the hydrolysis of inulin was observed. Moreover, we suggested that an increase of IOS would likely be due to the synthesis of the IOS by fructosyltransfer from 1-kestose to accumulated fructose and elongated fructose oligomers which can act as acceptors for fructan:fructan 1-fructosyltransferase (1-FFT). However, enzymes such as inulinase or fructan 1-exohydorolase (1-FEH) involved in inulin degradation in burdock roots are still not known. Here, we report the isolation and functional analysis of a gene encoding burdock 1-FEH.     

Dual supramolecular photochirogenesis: ultimate stereocontrol of photocyclodimerization by a chiral scaffold and confining host

In contrast to the brilliant success in thermal asymmetric synthesis, precise stereocontrol remains a great challenge in chiral photochemistry because of the lack of effective tools and methodologies for controlling the short-lived, weakly interacting, and highly reactive electronically excited species. In this work, we achieved this goal through the "dual-chiral, dual-supramolecular" photochirogenesis approach, which enabled us to realized dramatic acceleration and perfect stereocontrol in one of the most representative photoreactions. Thus, the [4 + 4] photocyclodimerization of 2-anthracenecarboxylate tethered to an α-cyclodextrin scaffold was accelerated by a γ-cyclodextrin or cucurbit[8]uril host and gave a single enantiomeric cyclodimer (out of four possible chiral and achiral stereoisomers) in up to 98% chemical and 99% optical yield.     

Experimental evidences for molecular origin of low-Q peak in neutron/x-ray scattering of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ionic liquids

Short- and long-range liquid structures of [C(n)mIm(+)][TFSA(-)] with n = 2, 4, 6, 8, 10, and 12 have been studied by high-energy x-ray diffraction (HEXRD) and small-angle neutron scattering (SANS) experiments with the aid of MD simulations. Observed x-ray structure factor, S(Q), for the ionic liquids with the alkyl-chain length n > 6 exhibited a characteristic peak in the low-Q range of 0.2-0.4 A?(-1), indicating the heterogeneity of their ionic liquids. SANS profiles I(H)(Q) and I(D)(Q) for the normal and the alkyl group deuterated ionic liquids, respectively, showed significant peaks for n = 10 and 12 without no form factor component for large spherical or spheroidal aggregates like micelles in solution. The peaks for n = 10 and 12 evidently disappeared in the difference SANS profiles ΔI(Q) [=I(D)(Q) - I(H)(Q)], although that for n = 12 slightly remained. This suggests that the long-range correlations originated from the alkyl groups hardly contribute to the low-Q peak intensity in SANS. To reveal molecular origin of the low-Q peak, we introduce here a new function; x-ray structure factor intensity at a given Q as a function of r, S(Q) (peak)(r). The S(Q) (peak)(r) function suggests that the observed low-Q peak intensity depending on n is originated from liquid structures at two r-region of 5-8 and 8-15 A? for all ionic liquids examined except for n = 12. Atomistic MD simulations are consistent with the HEXRD and SANS experiments, and then we discussed the relationship between both variations of low-Q peak and real-space structure with lengthening the alkyl group of the C(n)mIm.     

Gradient doping of conducting polymer films by means of bipolar electrochemistry

In this paper, we report a novel electrochemical doping method for conducting polymer films based on bipolar electrochemistry. The electrochemical doping of conducting polymers such as poly(3-methylthiophene) (PMT), poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(aniline) (PANI) on a bipolar electrode having a potential gradient on its surface successfully created gradually doped materials. In the case of PEDOT film, the color change at the anodic side was also observed to be gradually transparent. PANI film treated by the bipolar doping gave a multicolored gradation across the film. The results of UV-vis and energy dispersive X-ray analyses for the doped films supported the distribution of dopants in the polymer films reflecting the potential gradient on the bipolar electrode. Furthermore, the reversibility of the bipolar doping of the PMT film was demonstrated by a spectroelectrochemical investigation.     

Quantitative analysis of dissociation of LDH by high pressure native PAGE

ABSTRACT

High pressure native polyacrylamide gel electrophoresis has been designed to visualize the dissociation/association process of protein complexes. This paper reports this methodology in more quantitative way by inspecting pressure dissociation of pig heart lactate dehydrogenase, a tetrameric protein, which was extensively investigated in spectroscopic methods. We observed the change of electrophoresis pattern with pressure up to 150?MPa. By optimizing the buffer system and careful image analysis of the stained gels, we quantified all the dissociates in the process of pressurization. We discussed the characteristics of our methodology by comparing the result with the previously reported.     

Hydrostatic Pressure on Toroidal Interaction and Propeller Chirality of Hexaarylbenzenes: Explicit Solvent Effects on Differential Volumes in Methylcyclohexane and Hexane

A unique and effective interaction between the peripheral aromatic blades makes hexaarylbenzenes (HABs) attractive in fundamental research as well as for various applications such as molecular wires, sensors, and supramolecular assemblies. The chiroptical responses of HABs are susceptible to environmental factors such as solvent and temperature owing to the dynamic conformational transitions between the conformers. In this study, pressure dependence on the propeller chiral HABs in two different solvents was studied in detail. The effective differential volumes for two different equilibria were determined by quantitative analyses of CD spectra, affording very large differential volumes from the propeller to toroidal conformer (ΔV_T-C) of +43 and +42 cm³ mol⁻¹, for H2 and H6 , respectively, in methylcyclohexane. The value of H6 was further enhanced to +72 cm³ mol⁻¹ in hexane, the largest value for the typical unimolecular conformational change. Such a response of propeller chirality in HABs is expedient in designing more advanced piezo-sensitive materials.     

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs.