Supramolecular Zn(II)-Dipicolylamine-Azobenzene-Aminocyclodextrin-ATP Complex: Design and ATP Recognition in Water

Cyclodextrins (CyDs) are water-soluble host molecules possessing a nanosized hydrophobic cavity. In the realm of molecular recognition, this cavity is used not only as a recognition site but also as a reaction medium, where a hydrophobic sensor recognizes a guest molecule. Based on the latter concept, we have designed a novel supramolecular sensing system composed of Zn(II)-dipicolylamine metal complex-based azobenzene (1-Zn) and 3A-amino-3A-deoxy-(2AS,3AS)-γ-cyclodextrin (3-NH₂-γ-CyD) for sensing adenosine-5′-triphosphate (ATP). 1-Zn showed redshifts in the UV-Vis spectra and induced circular dichroism (ICD) only when both ATP and 3-NH₂-γ-CyD were present. Calculations of equilibrium constants indicated that the amino group of 3-NH₂-γ-CyD was involved in the formation of supramolecular 1-Zn/3-NH₂-γ-CyD/ATP. The Job plot of the ICD spectral response revealed that the stoichiometry of 1-Zn/3-NH₂-γ-CyD/ATP was 2:1:1. The pH effect was examined and 1-Zn/3-NH₂-γ-CyD/ATP was most stable in the neutral condition. The NOESY spectrum suggested the localization of 1-Zn in the 3-NH₂-γ-CyD cavity. Based on the obtained results, the metal coordination interaction of 1-Zn and the electrostatic interaction of 3-NH₂-γ-CyD were found to take place for ATP recognition. The “reaction medium approach” enabled us to develop a supramolecular sensing system that undergoes multi-point interactions in water. This study is the first step in the design of a selective sensing system based on a good understanding of supramolecular structures.     

A pre-heating vaporization technology of coal-water-slurry for the gasification process

A pre-heating vaporization technology of coal water slurry, CWS, was developed to increase the efficiency of coal gasification with the reduction of oxygen consumption. A CWS pre-heating experimental unit having a capacity of 2.0 tons-coal/day was manufactured. After the CWS was heated to 573 K at about 10 MPa, water in CWS was continuously vaporized in a tube of which the diameter increased gradually (2–10 mm I.D.), and dry coal particles with steam were atomized and fed to a vessel. No aggregation of coal particles was observed in the atomized samples. The temperature and the pressure distributions of the fluid were calculated with empirical heat transfer and pressure drop correlations. The calculated results well corresponded to the experimental data measured in some test points. Using the calculation model, a large scale apparatus of 100 tons-coal/day was designed using KNO₃ + NaNO₂ + NaNO₃ molten salt as a heating medium.     

Effect of molecular weight on molecular orientation and morphology of polypropylene sheets containing a β-nucleating agent

In this study, polypropylene (PP) films containing the β nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide, were prepared using PP with three different molecular weights (low, medium, and high) by extrusion process with T-shaped die. The structure and morphology of the films were studied after stretching. It was found that a unique molecular orientation, in which both the c-axis and crystalline lamellae were oriented perpendicular to the flow direction, was formed in all undrawn film samples, irrespective of the molecular weights of the PP. In the PP sheets stretched in the machine direction, the low-molecular-weight sample containing the nucleating agent exhibited brittle properties owing to a lack of tie chains in the stretching direction. In contrast, cavitation was prominent in the medium (M-PP)- and high (H-PP)-molecular-weight samples. Notably, M-PP containing the nucleating agent, with a high degree of molecular orientation, promoted the formation of a large number of voids. In H-PP containing the nucleating agent, the presence of numerous tie chains inhibited cavitation, resulting in fewer voids. The experimental results demonstrated the influence of the molecular weight on the void structure, which will be useful in the field of microporous membranes.     

Dominant stress region for crack initiation at interface edge of microdot on a substrate

In order to examine the mechanics of crack initiation at the free interface edge of a microcomponent on a substrate, delamination tests are carried out for two specimen shapes of Cr microdots on a SiO₂ substrate. The microdots of the first specimen are shaped like the frustum of a round cone. The Cr microdots are successfully delaminated from the SiO₂ substrate in a brittle manner and the critical load is measured by atomic force microscopy (AFM) with a lateral loading apparatus. Stress analysis reveals that a singular stress field exists near the interface edge and the strength for the crack initiation is governed by the intensified normal stress field. The critical stress intensity parameter is evaluated as K_σC ≈ 0.24 MPa m^0.39. Similar delamination tests are conducted for microdots shaped like the frustum of an oval cone. The stress distributions at the crack initiation of this specimen shape show a higher normal stress than the first specimen shape in the region near the interface edge of about x < 40 nm, while it is lower in the region of about x > 50 nm (x: distance from the edge). This suggests a limitation of conventional fracture mechanics: namely, the crack initiation in these specimens is not uniquely governed by the intensity of the singular field. It is found that the delamination crack is initiated when the averaged stress σ_ya in the region of 90-130 nm reaches 190-270 MPa, regardless of the specimen shape. This indicates that the dominant stress region of crack initiation is roughly estimated as 90-130 nm and the criterion is given in terms of the averaged stress in the region.     

Space–time interface-tracking with topology change (ST-TC)

To address the computational challenges associated with contact between moving interfaces, such as those in cardiovascular fluid–structure interaction (FSI), parachute FSI, and flapping-wing aerodynamics, we introduce a space–time (ST) interface-tracking method that can deal with topology change (TC). In cardiovascular FSI, our primary target is heart valves. The method is a new version of the deforming-spatial-domain/stabilized space–time (DSD/SST) method, and we call it ST-TC. It includes a master–slave system that maintains the connectivity of the “parent” mesh when there is contact between the moving interfaces. It is an efficient, practical alternative to using unstructured ST meshes, but without giving up on the accurate representation of the interface or consistent representation of the interface motion. We explain the method with conceptual examples and present 2D test computations with models representative of the classes of problems we are targeting.     

Diffusion Magnetic Resonance Imaging-Based Biomarkers for Neurodegenerative Diseases

There has been an increasing prevalence of neurodegenerative diseases with the rapid increase in aging societies worldwide. Biomarkers that can be used to detect pathological changes before the development of severe neuronal loss and consequently facilitate early intervention with disease-modifying therapeutic modalities are therefore urgently needed. Diffusion magnetic resonance imaging (MRI) is a promising tool that can be used to infer microstructural characteristics of the brain, such as microstructural integrity and complexity, as well as axonal density, order, and myelination, through the utilization of water molecules that are diffused within the tissue, with displacement at the micron scale. Diffusion tensor imaging is the most commonly used diffusion MRI technique to assess the pathophysiology of neurodegenerative diseases. However, diffusion tensor imaging has several limitations, and new technologies, including neurite orientation dispersion and density imaging, diffusion kurtosis imaging, and free-water imaging, have been recently developed as approaches to overcome these constraints. This review provides an overview of these technologies and their potential as biomarkers for the early diagnosis and disease progression of major neurodegenerative diseases.     

Melatonin-Induced Postconditioning Suppresses NMDA Receptor through Opening of the Mitochondrial Permeability Transition Pore via Melatonin Receptor in Mouse Neurons

Mitochondrial membrane potential regulation through the mitochondrial permeability transition pore (mPTP) is reportedly involved in the ischemic postconditioning (PostC) phenomenon. Melatonin is an endogenous hormone that regulates circadian rhythms. Its neuroprotective effects via mitochondrial melatonin receptors (MTs) have recently attracted attention. However, details of the neuroprotective mechanisms associated with PostC have not been clarified. Using hippocampal CA1 pyramidal cells from C57BL mice, we studied the involvement of MTs and the mPTP in melatonin-induced PostC mechanisms similar to those of ischemic PostC. We measured changes in spontaneous excitatory postsynaptic currents (sEPSCs), intracellular calcium concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents after ischemic challenge, using the whole-cell patch-clamp technique. Melatonin significantly suppressed increases in sEPSCs and intracellular calcium concentrations. The NMDAR currents were significantly suppressed by melatonin and the MT agonist, ramelteon. However, this suppressive effect was abolished by the mPTP inhibitor, cyclosporine A, and the MT antagonist, luzindole. Furthermore, both melatonin and ramelteon potentiated depolarization of mitochondrial membrane potentials, and luzindole suppressed depolarization of mitochondrial membrane potentials. This study suggests that melatonin-induced PostC via MTs suppressed the NMDAR that was induced by partial depolarization of mitochondrial membrane potential by opening the mPTP, reducing excessive release of glutamate and inducing neuroprotection against ischemia-reperfusion injury.     

Size-dependent separation of graphene oxide by deformation of packed-gel in a chromatographic column

ABSTRACT

A deformable gel-packed chromatographic column was used to separate as-synthesized graphite oxide with different sizes. The synthesized gel (56 µm) was deformed by pressure of the fluid flow and the gaps in the gels showed a range of sizes. A suspension of graphene oxide (0.1 g/L, 10 mL) was injected, and graphene oxide in the elution had a size at 0.56 μm and 0.14 μm, whereas in half upper and bottom domain of the gel layer graphene oxide had a size at 33 µm and 2.9 µm, respectively, demonstrating that graphene oxide suspension was separated by size through gel layer.     

Multifunctional Initiator with Platinum-Acetylide Dendritic Core for Living Polymerization of Isocyanides

A novel multifunctional initiator has been developed by peripheral modification of a Pt-acetylide dendrimer. Pd–Pt μ-ethynediyl units were introduced to the first-generation dendrimer by a divergent method. The dendritic initiator was applicable to the living polymerization of aryl isocyanides, producing high molecular weight polymers with a narrow polydispersity index in quantitative yields. The ³¹P NMR spectrum of the resulting polymer suggested that all Pd–Pt μ-ethynediyl units in the dendritic molecule actually functioned as an initiator.