3D Structural Insights into β-Glucans and Their Binding Proteins

β(1,3)-glucans are a component of fungal and plant cell walls. The β-glucan of pathogens is recognized as a non-self-component in the host defense system. Long β-glucan chains are capable of forming a triple helix structure, and the tertiary structure may profoundly affect the interaction with β-glucan-binding proteins. Although the atomic details of β-glucan binding and signaling of cognate receptors remain mostly unclear, X-ray crystallography and NMR analyses have revealed some aspects of β-glucan structure and interaction. Here, we will review three-dimensional (3D) structural characteristics of β-glucans and the modes of interaction with β-glucan-binding proteins.     

Acetic Acid-Catalyzed Formation of N-Phenylphthalimide from Phthalanilic Acid: A Computational Study of the Mechanism

In glacial acetic acid, phthalanilic acid and its monosubstituents are known to be converted to the corresponding phthalimides in relatively good yields. In this study, we computationally investigated the experimentally proposed two-step (addition-elimination or cyclization-dehydration) mechanism at the second-order Møller-Plesset perturbation (MP2) level of theory for the unsubstituted phthalanilic acid, with an explicit acetic acid molecule included in the calculations. In the first step, a gem-diol tetrahedral intermediate is formed by the nucleophilic attack of the amide nitrogen. The second step is dehydration of the intermediate to give N-phenylphthalimide. In agreement with experimental findings, the second step has been shown to be rate-determining. Most importantly, both of the steps are catalyzed by an acetic acid molecule, which acts both as proton donor and acceptor. The present findings, along with those from our previous studies, suggest that acetic acid and other carboxylic acids (in their undissociated forms) can catalyze intramolecular nucleophilic attacks by amide nitrogens and breakdown of the resulting tetrahedral intermediates, acting simultaneously as proton donor and acceptor. In other words, double proton transfers involving a carboxylic acid molecule can be part of an extensive bond reorganization process from cyclic hydrogen-bonded complexes.     

Characterisation of the Dynamic Interactions between Complex N-Glycans and Human CD22

CD22 (Siglec-2) is a B-cell surface inhibitory protein capable of selectively recognising sialylated glycans, thus dampening autoimmune responses against self-antigens. Here we have characterised the dynamic recognition of complex-type N-glycans by human CD22 by means of orthogonal approaches including NMR spectroscopy, computational methods and biophysical assays. We provide new molecular insights into the binding mode of sialoglycans in complex with h-CD22, highlighting the role of the sialic acid galactose moieties in the recognition process, elucidating the conformational behaviour of complex-type N-glycans bound to Siglec-2 and dissecting the formation of CD22 homo-oligomers on the B-cell surface. Our results could enable the development of additional therapeutics capable of modulating the activity of h-CD22 in autoimmune diseases and malignancies derived from B-cells.     

Chiral lewis acid-catalyzed enantioselective michael reactions in water

Asymmetric Michael reactions of ß-ketoesters with enones were effectively catalyzed by complexes of silver salts and BINAP derivatives in water. The reactions have proved to give Michael adducts in high yields with high enantioselectivities. These reactions are the first example of Lewis acid-catalyzed asymmetric Michael reactions in water.     

Effects of supplied gas humidity change on PEFC transient power generation

Polymer electrolyte fuel cells (PEFCs, PEMFCs) are gaining increasingly more attention as clean and efficient energy‐conversion devices. Vapor and liquid transport has a strong impact on the power generation characteristics and efficiency of PEFCs, and so proper water management is needed for efficiency and durability. However, water transport factors are not well understood, particularly during unsteady operation—often the case in vehicles and distributed stationary power generators. In this study, to understand and generalize the effects of local water transport on PEFC performance, transient mass transport characteristics inside a PEFC were investigated experimentally and numerically. For this purpose, we developed an unsteady two‐dimensional numerical model based on mass‐ and charge‐conservation equations in the channel, gas diffusion layer (GDL), and membrane electrode assembly (MEA). As necessary parameters for model development, we measured the water content of the MEA, the membrane resistivity, the activation overvoltage, overall mass transfer coefficient, and so on. The membrane resistivity greatly increases as the relative humidity decreases. The activation overvoltage is also affected by the relative humidity, and not only by the current density and oxygen activity. Current load and voltage changes are frequently used as PEFC transient inputs, but lead to very complicated and intractable phenomena such as changes in the amount of generated water and electro‐osmosis, state of the electrical double layer, and so on. Hence, stepwise changes in the relative humidity of the supplied gas were adopted in this study. The experimental and numerical transient responses were in good agreement under most operating conditions, and the reliability of our measurement methods for the water transport properties and our numerical model were confirmed. Here we discuss the dominant factor in the transient responses, and conclude that the transport resistance at the PEM–GDL interface is the largest and most dominant factor in a relatively dry state under unsteady operating conditions. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20371     

Removal of selected pharmaceuticals by chlorination, coagulation-sedimentation and powdered activated carbon treatment

Removal property of nine pharmaceuticals (clofibric acid, diclofenac, fenoprofen, gemfibrozil, ibuprofen, indomethacin, ketoprofen, naproxen and propyphenazone) by chlorination, coagulation-sedimentation and powdered activated carbon treatment was examined by laboratory-scale experiments under the conditions close to actual drinking water treatment processes. Indomethacin and propyphenazone were completely degraded by chlorination within 30 minutes, but others remained around 30% (naproxen and diclofenac) or more than 80% of the initial concentration after 24 hours. A couple of unidentified peaks in a chromatogram of the chlorinated samples suggested the formation of unknown chlorination by-products. Competitive adsorption was observed when the mixed solution of the target pharmaceuticals was subjected to batch adsorption test with powdered activated carbon. Clofibric acid and ibuprofen, which were relatively less hydrophobic among the nine compounds, persisted around 60% of the initial concentration after 3 hours of contact time. Removal performance in actual drinking water treatment would become lower due to existence of other competitive substances in raw water (e.g. natural organic matter). Coagulation-sedimentation using polyaluminium chloride hardly removed most of the pharmaceuticals even under its optimal dose for turbidity removal. It is suggested that the most part of pharmaceuticals in raw water might persist in the course of conventional drinking water treatments.     

Relationship between Ba atom emission and electrode temperature in a low-pressure fluorescent lamp

A relationship between emission characteristics of Ba atom as an emitter material and temperature distributions of an electrode in a fluorescent lamp is described, which is measured by using laser-induced fluorescence and black-body radiation method, respectively. In a virgin lamp, a hot spot observed at the electrode edge connected to the power supply is the main source of Ba atom emission. In a long-term-used lamp, it is shown that Ba atom emission, thermionic electron emission in cathode half-cycle and electron collection in anode half-cycle are most active on the hot spot appearing on the center of the electrode.     

Spatial correlation coefficients of rainfall intensity inferred from statistics of rainfall intensity and rain attenuation

On the basis of the reliable statistics of rainfall rate and rainfall attenuation for 8 localities in Europe, the spatial correlation coefficient of point rainfall intensity was inferred for each locality from the cumulative distributions of attenuation and rainfall intensity by inversely applying the modified Morita and Higuti rainfall attenuation prediction method. It was found that for European regions the spatial correlation coefficient with an exponential dependence on the horizontal distance is more appropriate for the prediction of rainfall attenuation than that proposed by Morita and Higuti for the Japanese climate. It was also found that although the spatial correlation characteristic varies significantly from one locality to another its variance is not so significant within a particular ccir rainfall climatic zone. This suggests that in predicting the rainfall attenuation it is desirable to employ the spatial correlation coefficient appropriate for the locality to be estimated.     

Epitaxial growth of titanium oxide thin films on MgO(100) single-crystal substrates by reactive deposition methods

We synthesized titanium oxide thin films on MgO(100) single-crystal substrates by two reactive deposition methods and compared the structures of the thin films formed by these methods. In one method (pulsed-molecular-beam deposition method), molecular oxygen is supplied to the substrates by using a pulsed-molecular-oxygen beam source and deposition of one unit layer of titanium and subsequent supply of molecular oxygen are repeatedly performed. In the other method (radical beam deposition method), atomic oxygen is irradiated to the substrates by using an atomic oxygen beam generated by the radical beam source and irradiation of the atomic oxygen and deposition of titanium are simultaneously performed. In the case of the pulsed-molecular-beam deposition method, the crystal structure was changed by increasing the number of oxygen pulses supplied from the beam source. We found that the crystal structure of titanium oxide depended on the composition ratio of O:Ti in the film. The maximum ratio of O:Ti attainable by this method was 1.85, and at this ratio, (100)-oriented pseudorutile was formed. In the case of the radical beam deposition method, (100)-oriented anatase was formed below the titanium deposition rate of 0.10 nm/s and pseudorutile (TiO_2−δ) was formed above 0.15 nm/s. The pseudorutile structure synthesized on this experiment was very stable in air. We concluded that the crystal structure of the pseudorutile is a new crystal structure of titanium oxide.