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12 pages, 2248 KiB

Open AccessArticle

Use of a Longer Aglycon Moiety Bearing Sialyl α(2→3) Lactoside on the Glycopolymer for Lectin Evaluation

by Ryota Adachi, Takahiko Matsushita, Tetsuo Koyama, Ken Hatano and Koji Matsuoka

Polymers 2023, 15(4), 998; https://doi.org/10.3390/polym15040998 - 17 Feb 2023

Cited by 1 | Viewed by 1729

A polymerizable alcohol having 9 PEG repeats was prepared in order to mimic an oligosaccharide moiety. Sialyl α(2→3) lactose, which is known as a sugar moiety of GM3 ganglioside, was also prepared, and the polymerizable alcohol was condensed with the sialyl α(2→3) lactose [...] Read more.

A polymerizable alcohol having 9 PEG repeats was prepared in order to mimic an oligosaccharide moiety. Sialyl α(2→3) lactose, which is known as a sugar moiety of GM3 ganglioside, was also prepared, and the polymerizable alcohol was condensed with the sialyl α(2→3) lactose derivative to afford the desired glycomonomer, which was further polymerized with or without acrylamide to give water-soluble glycopolymers. The glycopolymers had higher affinities than those of glycopolymers having sialyl lactose moieties with shorter aglycon moieties. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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7 pages, 795 KiB

Open AccessBrief Report

Emergence of Drift Variants That May Affect COVID-19 Vaccine Development and Antibody Treatment

by Takahiko Koyama, Dilhan Weeraratne, Jane L. Snowdon and Laxmi Parida

Pathogens 2020, 9(5), 324; https://doi.org/10.3390/pathogens9050324 - 26 Apr 2020

Cited by 171 | Viewed by 37814

Abstract

New coronavirus (SARS-CoV-2) treatments and vaccines are under development to combat COVID-19. Several approaches are being used by scientists for investigation, including (1) various small molecule approaches targeting RNA polymerase, 3C-like protease, and RNA endonuclease; and (2) exploration of antibodies obtained from convalescent [...] Read more.

New coronavirus (SARS-CoV-2) treatments and vaccines are under development to combat COVID-19. Several approaches are being used by scientists for investigation, including (1) various small molecule approaches targeting RNA polymerase, 3C-like protease, and RNA endonuclease; and (2) exploration of antibodies obtained from convalescent plasma from patients who have recovered from COVID-19. The coronavirus genome is highly prone to mutations that lead to genetic drift and escape from immune recognition; thus, it is imperative that sub-strains with different mutations are also accounted for during vaccine development. As the disease has grown to become a pandemic, B-cell and T-cell epitopes predicted from SARS coronavirus have been reported. Using the epitope information along with variants of the virus, we have found several variants which might cause drifts. Among such variants, 23403A>G variant (p.D614G) in spike protein B-cell epitope is observed frequently in European countries, such as the Netherlands, Switzerland, and France, but seldom observed in China. Full article

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13 pages, 3221 KiB

Open AccessArticle

Preparation of Functional Monomers as Precursors of Bioprobes from a Common Styrene Derivative and Polymer Synthesis

by Riho Hayama, Tetsuo Koyama, Takahiko Matsushita, Ken Hatano and Koji Matsuoka

Molecules 2018, 23(11), 2875; https://doi.org/10.3390/molecules23112875 - 4 Nov 2018

Cited by 11 | Viewed by 3896

Abstract

CM-Str (4-(Chloromethyl)styrene) was used as a useful starting material for the construction of a series of functional monomers. Substitution of the chlorine to the corresponding azide was performed, and the reduction of the azide proceeded smoothly to afford an aminostyrene, which was used [...] Read more.

CM-Str (4-(Chloromethyl)styrene) was used as a useful starting material for the construction of a series of functional monomers. Substitution of the chlorine to the corresponding azide was performed, and the reduction of the azide proceeded smoothly to afford an aminostyrene, which was used as a common precursor for the preparation of functional monomers. Condensation of the amine with a fluorophore, biotin and carbohydrate was accomplished. Among the monomers, a carbohydrate monomer was polymerized with or without acrylamide as a model polymerization to yield the corresponding water-soluble glycopolymers, and biological evaluations of the glycopolymers for a lectin, and wheat germ agglutinin (WGA), were carried out on the basis of the fluorescence change of tryptophan in the WGA. Full article

(This article belongs to the Section Bioorganic Chemistry)

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15 pages, 2558 KiB

Open AccessArticle

Numerical Investigation of Small-Scale Adsorption Cooling System Performance Employing Activated Carbon-Ethanol Pair

by Marzia Khanam, Skander Jribi, Takahiko Miyazaki, Bidyut Baran Saha and Shigeru Koyama

Energies 2018, 11(6), 1499; https://doi.org/10.3390/en11061499 - 8 Jun 2018

Cited by 23 | Viewed by 5329

Abstract

Adsorber heat exchanger design has great importance in increasing the performance of the adsorption-based cooling system. In this study, a transient two-dimensional axisymmetric Computational Fluid Dynamics (CFD) model has been developed for the performance investigation of finned tube type adsorber using activated carbon [...] Read more.

Adsorber heat exchanger design has great importance in increasing the performance of the adsorption-based cooling system. In this study, a transient two-dimensional axisymmetric Computational Fluid Dynamics (CFD) model has been developed for the performance investigation of finned tube type adsorber using activated carbon and ethanol as the working pair. The operating conditions of the cooling system were 15, 20 and 80 for evaporation, cooling and heating temperatures, respectively. The simulated temperature profiles for different adsorbent thicknesses were validated with those from experimental data measured in our laboratory. Moreover, the error in mass and energy balance were 3% and 7.88%, respectively. Besides, the performance investigation has been performed for cycle time ranging from 600 s to 1400 s. The optimum cycle time was 800 s and the corresponding evaluated specific cooling power (SCP) and coefficient of performance (COP) were found to be 488 W/kg and 0.61, respectively. The developed CFD model will be used for fin height and fin pitch optimization and can be extended to other adsorbent-adsorbate based adsorption cooling system. Full article

(This article belongs to the Section A: Sustainable Energy)

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17 pages, 3578 KiB

Open AccessArticle

Exergy Analysis of Serpentine Thermosyphon Solar Water Heater

by Muhammad Faisal Hasan, Md. Sayeed Ur Rahim Mahadi, Takahiko Miyazaki, Shigeru Koyama and Kyaw Thu

Appl. Sci. 2018, 8(3), 391; https://doi.org/10.3390/app8030391 - 7 Mar 2018

Cited by 16 | Viewed by 7505

Abstract

The performance of a solar hot water system is assessed for heat pump and domestic heating applications. Thermodynamic analysis on a serpentine-type thermosyphon flat-plate solar heater is conducted using the Second Law of thermodynamics. Exergetic optimization is first performed to determine the parameters [...] Read more.

The performance of a solar hot water system is assessed for heat pump and domestic heating applications. Thermodynamic analysis on a serpentine-type thermosyphon flat-plate solar heater is conducted using the Second Law of thermodynamics. Exergetic optimization is first performed to determine the parameters for the maximum exergy efficiency using MATLAB optimization toolbox. Geometric parameters (collector surface area, dimensions, and pipe diameter), optical parameters (transmittance absorptance product), ambient temperature, solar irradiation and operating parameters (mass flow rate, fluid temperature, and overall heat transfer (loss) coefficient) are accounted for in the optimization scheme. The exergy efficiency at optimum condition is found to be 3.72%. The results are validated using experimental data and found to be in good agreement. The analysis is further extended to the influence of various operating parameters on the exergetic efficiency. It is observed that optical and thermal exergy losses contribute almost 20%, whereas approximately 77% exergy destruction is contributed by the thermal energy conversion. Exergy destruction due to pressure drop is found negligible. The result of this analysis can be used for designing and optimization of domestic heat pump system and hot water application. Full article

(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)

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14 pages, 2885 KiB

Open AccessFeature PaperArticle

Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

by Indri Yaningsih, Agung Tri Wijayanta, Takahiko Miyazaki and Shigeru Koyama

Appl. Sci. 2018, 8(2), 181; https://doi.org/10.3390/app8020181 - 26 Jan 2018

Cited by 21 | Viewed by 4996

Abstract

The impact of double-sided delta-winglet tape (DWTs) inserts on convective heat transfer and friction behaviors in a tube was experimentally investigated. Three DWTs with ratios of winglet-height (b) to inner tube diameter (d_i) called blockage ratio (R [...] Read more.

The impact of double-sided delta-winglet tape (DWTs) inserts on convective heat transfer and friction behaviors in a tube was experimentally investigated. Three DWTs with ratios of winglet-height (b) to inner tube diameter (d_i) called blockage ratio (R_b) of 0.28, 0.35 and 0.42 were tested and their performance was compared to that of a longitudinal strip and plain tube under similar test flow conditions. Experiments were conducted over a wide range of flow rates, 3.35 × 10⁻⁵–8.33 × 10⁻⁵ m³/s, which correspond to 5500 ≤ Reynolds number (Re) ≤ 14,500 in the 14.3 mm i.d. tube. The results revealed that using DWTs dramatically increased the Nusselt number (Nu) by as much as 364.3% and the friction factor (f) by 15.5 times compared with those of a plain tube. Thermal performance (η) increased with a corresponding increase in R_b. The highest thermal performance (η) obtained was 1.4. Showing a notable improvement on the thermal performance of the system, DWTs are proposed as a favorable insert device. Full article

(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)

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13 pages, 748 KiB

Open AccessArticle

Sod1 Loss Induces Intrinsic Superoxide Accumulation Leading to p53-Mediated Growth Arrest and Apoptosis

by Kenji Watanabe, Shuichi Shibuya, Hirofumi Koyama, Yusuke Ozawa, Toshihiko Toda, Koutaro Yokote and Takahiko Shimizu

Int. J. Mol. Sci. 2013, 14(6), 10998-11010; https://doi.org/10.3390/ijms140610998 - 24 May 2013

Cited by 30 | Viewed by 8664

Abstract

Oxidative damages induced by a redox imbalance cause age-related changes in cells and tissues. Superoxide dismutase (SOD) enzymes play a major role in the antioxidant system and they also catalyze superoxide radicals (O₂^·⁻). Since the loss of cytoplasmic SOD [...] Read more.

Oxidative damages induced by a redox imbalance cause age-related changes in cells and tissues. Superoxide dismutase (SOD) enzymes play a major role in the antioxidant system and they also catalyze superoxide radicals (O₂^·⁻). Since the loss of cytoplasmic SOD (SOD1) resulted in aging-like phenotypes in several types of mouse tissue, SOD1 is essential for the maintenance of tissue homeostasis. To clarify the cellular function of SOD1, we investigated the cellular phenotypes of Sod1-deficient fibroblasts. We demonstrated that Sod1 deficiency impaired proliferation and induced apoptosis associated with O₂^·⁻ accumulation in the cytoplasm and mitochondria in fibroblasts. Sod1 loss also decreased the mitochondrial membrane potential and led to DNA damage-mediated p53 activation. Antioxidant treatments effectively improved the cellular phenotypes through suppression of both intracellular O₂^·⁻ accumulation and p53 activation in Sod1-deficient fibroblasts. In vivo experiments revealed that transdermal treatment with a vitamin C derivative significantly reversed the skin thinning commonly associated with the upregulated p53 action in the skin. Our findings revealed that intrinsic O₂^·⁻ accumulation promoted p53-mediated growth arrest and apoptosis as well as mitochondrial disfunction in the fibroblasts. Full article

(This article belongs to the Special Issue Oxidative Stress and Ageing)

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11 pages, 640 KiB

Open AccessReview

Antioxidants Improve the Phenotypes of Dilated Cardiomyopathy and Muscle Fatigue in Mitochondrial Superoxide Dismutase-Deficient Mice

by Hirofumi Koyama, Hidetoshi Nojiri, Satoru Kawakami, Tadahiro Sunagawa, Takuji Shirasawa and Takahiko Shimizu

Molecules 2013, 18(2), 1383-1393; https://doi.org/10.3390/molecules18021383 - 24 Jan 2013

Cited by 38 | Viewed by 7453

Abstract

Redox imbalance elevates the reactive oxygen species (ROS) level in cells and promotes age-related diseases. Superoxide dismutases (SODs) are antioxidative enzymes that catalyze the degradation of ROS. There are three SOD isoforms: SOD1/CuZn-SOD, SOD2/Mn-SOD, and SOD3/EC-SOD. SOD2, which is localized in the mitochondria, [...] Read more.

Redox imbalance elevates the reactive oxygen species (ROS) level in cells and promotes age-related diseases. Superoxide dismutases (SODs) are antioxidative enzymes that catalyze the degradation of ROS. There are three SOD isoforms: SOD1/CuZn-SOD, SOD2/Mn-SOD, and SOD3/EC-SOD. SOD2, which is localized in the mitochondria, is an essential enzyme required for mouse survival, and systemic knockout causes neonatal lethality in mice. To investigate the physiological function of SOD2 in adult mice, we generated a conditional Sod2 knockout mouse using a Cre-loxP system. When Sod2 was specifically deleted in the heart and muscle, all mice exhibited dilated cardiomyopathy (DCM) and died by six months of age. On the other hand, when Sod2 was specifically deleted in the skeletal muscle, mice showed severe exercise disturbance without morphological abnormalities. These provide useful model of DCM and muscle fatigue. In this review, we summarize the impact of antioxidants, which were able to regulate mitochondrial superoxide generation and improve the phenotypes of the DCM and the muscle fatigue in mice. Full article

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