Publications by authors named "Osamu Kubo"

We undertook an optimization effort involving propan-2-yl 4-({6-[5-(methanesulfonyl)-2,3-dihydro-1H-indol-1-yl]pyrimidin-4-yl}oxy)piperidine-1-carboxylate 1, which we had previously discovered as a novel G protein-coupled receptor 119 (GPR119) agonist. To occupy a presumed hydrophobic space between the pyrimidine and piperidine rings in interaction with GPR119, we replaced the linker oxygen with nitrogen. Subsequently, the introduction of a substituent at the bridging nitrogen atom was explored.

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We previously identified a novel series of indolinylpyrimidine derivatives exemplified by 2 in Figure 1, which is an indoline based derivative, as potent GPR119 agonists. Despite the attractive potency of 2, this compound inhibited the human ether-a-go-go-related gene (hERG) K channel. We elucidated crucial roles of the methylsulfonyl group of 2 in its interaction with the hERG channel and the GPR119 receptor, presumably as a hydrogen bond acceptor (HBA).

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Some gas sensors exhibit significant increases in their sensitivity and response/recovery rates under light illumination. This photoactivation of the gas response is considered a promising alternative to conventional thermal activation, which requires high power consumption. Thin layers of molybdenum disulfide (MoS) are known to exhibit an effective photoactivated gas response under visible light.

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Article Synopsis
  • The study explores the gas-sensing capabilities of a van der Waals heterojunction made from graphene and a MoS flake, focusing on its sensitivity to nitrogen monoxide (NO) gas.
  • Researchers ensured accurate measurements by passivating non-relevant areas, revealing that the device's resistance changed significantly (over 10 times) when exposed to 1 ppm NO under specific electrical conditions.
  • The sensor's response varied depending on the applied reverse bias and back-gate voltages, showing improved sensitivity with increased reverse bias but reduced response at high forward bias or positive back-gate voltage.
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Acyl CoA:monoacylglycerol acyltransferase-2 (MGAT2) has emerged as a potential peripheral target for the treatment of obesity and metabolic disorders. We previously identified a novel series of N-phenylindoline-5-sulfonamide derivatives exemplified by 2 as potent and orally bioavailable MGAT2 inhibitors. Despite its attractive potency, further assessment revealed that this compound exhibited time-dependent inhibition (TDI) of cytochrome P450 3A4 (CYP3A4).

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Acyl CoA:monoacylglycerol acyltransferase-2 (MGAT2) has attracted interest as a novel target for the treatment of obesity and metabolic diseases. Starting from N-phenylbenzenesulfonamide derivative 1 with moderate potency for MGAT2 inhibition, we explored an effective location of the hydrophobic group at the 1-position to enhance MGAT2 inhibitory activity. Shifting the hydrophobic group to the adjacent position followed by introduction of a bicyclic central core to restrict the substituent orientation produced N-phenylindoline-5-sulfonamide derivative 10b, which displayed much improved potency, with an IC50 value of 1.

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The synthesis of silicene, graphene-like silicon, has generated very strong interest. Here, we reveal the growth of high aspect ratio, perfectly straight, and aligned silicon nanoribbons, exhibiting pyramidal cross section. They are multistacks of silicene and show in angle-resolved photoemission cone-like dispersion of their π and π* bands, at the X[overline] point of their one-dimensional Brillouin zone, with Fermi velocity of ~1.

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Adsorption and electronic structure of octithiophene (8T) molecules on Cu(III) and Au(III) surfaces are investigated using scanning tunneling microscopy (STM) and spectroscopy (STS) at room temperature. We find a large difference in adsorption behavior of 8T molecules on the two surfaces. At the initial stage of adsorption, 8T molecules are stabilized in the form of molecular chain on a terrace of Cu(III), whereas neither such chain structure nor isolated 8T molecules have been observed on a terrace of Au(III).

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In the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement.

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Four-terminal electrical measurement is realized on a microscopic structure in air, without a lithographic process, using a home-built quadruple-scanning-probe force microscope (QSPFM). The QSPFM has four probes whose positions are individually controlled by obtaining images of a sample in the manner of atomic force microscopy (AFM), and uses the probes as contacting electrodes for electrical measurements. A specially arranged tuning fork probe (TFP) is used as a self-detection force sensor to operate each probe in a frequency modulation AFM mode, resulting in simultaneous imaging of the same microscopic feature on an insulator using the four TFPs.

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We expand the range of applications of a tuning fork probe (TFP) in frequency-modulation atomic force microscopy (FM-AFM) by attaching a long metal tip at a certain angle. By the combined flexure of the metal tip and the tuning fork prong, this TFP can change the direction of the detectable force by switching the resonance frequency, which has not been realized with conventional TFPs with short tips. The oscillatory behavior of the tip apex of the TFP is predicted by computer simulations and is experimentally confirmed with scanning electron microscope.

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Background: A 6-year-old girl with Rasmussen syndrome (RS) showed multiple small high-signal-intensity areas independently in the right hemisphere by fluid-attenuated inversion recovery (FLAIR) imaging on magnetic resonance imaging (MRI) 1 year after the onset of epilepsy.

Methods: MRI performed 4 months later demonstrated a further increase in the number of these foci and enlargement in the size of the previous FLAIR lesions.

Results: An [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) study showed a strong, spotty uptake in the right temporooccipital regions, corresponding to the sites of continuous EEG seizure discharges.

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