271 results on '"Youngjo Kim"'
Search Results
2. The Interplay between Oxidative Stress and the Nuclear Lamina Contributes to Laminopathies and Age-Related Diseases
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Lidya Kristiani and Youngjo Kim
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lamins ,laminopathy ,HGPS ,oxidative stress ,DNA damage ,senescence ,Cytology ,QH573-671 - Abstract
Oxidative stress is a physiological condition that arises when there is an imbalance between the production of reactive oxygen species (ROS) and the ability of cells to neutralize them. ROS can damage cellular macromolecules, including lipids, proteins, and DNA, leading to cellular senescence and physiological aging. The nuclear lamina (NL) is a meshwork of intermediate filaments that provides structural support to the nucleus and plays crucial roles in various nuclear functions, such as DNA replication and transcription. Emerging evidence suggests that oxidative stress disrupts the integrity and function of the NL, leading to dysregulation of gene expression, DNA damage, and cellular senescence. This review highlights the current understanding of the interplay between oxidative stress and the NL, along with its implications for human health. Specifically, elucidation of the mechanisms underlying the interplay between oxidative stress and the NL is essential for the development of effective treatments for laminopathies and age-related diseases.
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- 2023
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3. Recent Advances in Counterfeit Art, Document, Photo, Hologram, and Currency Detection Using Hyperspectral Imaging
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Shuan-Yu Huang, Arvind Mukundan, Yu-Ming Tsao, Youngjo Kim, Fen-Chi Lin, and Hsiang-Chen Wang
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hyperspectral imaging ,forgery detection ,artwork authentication ,document authentication ,counterfeit currency detection ,photo authentication ,Chemical technology ,TP1-1185 - Abstract
Forgery and tampering continue to provide unnecessary economic burdens. Although new anti-forgery and counterfeiting technologies arise, they inadvertently lead to the sophistication of forgery techniques over time, to a point where detection is no longer viable without technological aid. Among the various optical techniques, one of the recently used techniques to detect counterfeit products is HSI, which captures a range of electromagnetic data. To aid in the further exploration and eventual application of the technique, this study categorizes and summarizes existing related studies on hyperspectral imaging and creates a mini meta-analysis of this stream of literature. The literature review has been classified based on the product HSI has used in counterfeit documents, photos, holograms, artwork, and currency detection.
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- 2022
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4. Role of lamins in 3D genome organization and global gene expression
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Youngjo Kim, Xiaobin Zheng, and Yixian Zheng
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3d genome ,hi-c ,hilands ,lads ,tads ,lamin ,nuclear lamina ,Genetics ,QH426-470 ,Cytology ,QH573-671 - Abstract
Genome-wide mapping of lamin-B1-genome interactions has shown that gene-poor and transcriptionally inactive genomic regions are associated with the nuclear lamina. Numerous studies have suggested that lamins, the major structural components of the nuclear lamina, play a role in global chromatin organization and gene expression. How lamins could influence the 3D genome organization and transcription from the nuclear periphery has, however, remained unclear. Our recent studies showed that lamins differentially regulate distinct lamina-associated chromatin domains (LADs) at the nuclear periphery, which can in turn influence global 3D genome organization and gene expression. In this Extra View, we discuss how by using various genomics tools, it has become possible to reveal the functions of lamins in orchestrating 3D genome organization and gene expression. Abbreviations: 3D: three dimensional; LAD: lamina-associated chromatin domain; 3C: Chromosome Conformation Capture; TAD: topologically associated domain; HiLands: Histone and lamina landscape; NL: nuclear lamina; mESC: mouse embryonic stem cell; DamID: DNA adenine methyltransferase identification;
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- 2019
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5. RIPK3 Contributes to Lyso-Gb3-Induced Podocyte Death
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So-Young Kim, Samel Park, Seong-Woo Lee, Ji-Hye Lee, Eun Soo Lee, Miri Kim, Youngjo Kim, Jeong Suk Kang, Choon Hee Chung, Jong-Seok Moon, and Eun Young Lee
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Fabry disease ,lyso-Gb3 ,alpha-galactosidase A ,RIPK3 ,necroptosis ,alpha-galactosidase ,Cytology ,QH573-671 - Abstract
Fabry disease is a lysosomal storage disease with an X-linked heritage caused by absent or decreased activity of lysosomal enzymes named alpha-galactosidase A (α-gal A). Among the various manifestations of Fabry disease, Fabry nephropathy significantly affects patients’ morbidity and mortality. The cellular mechanisms of kidney damage have not been elusively described. Necroptosis is one of the programmed necrotic cell death pathways and is known to play many important roles in kidney injury. We investigated whether RIPK3, a protein phosphokinase with an important role in necroptosis, played a crucial role in the pathogenesis of Fabry nephropathy both in vitro and in vivo. The cell viability of podocytes decreased after lyso-Gb3 treatment in a dose-dependent manner, with increasing RIPK3 expression. Increased reactive oxygen species (ROS) generation after lyso-Gb3 treatment, which was alleviated by GSK’872 (a RIPK3 inhibitor), suggested a role of oxidative stress via a RIPK3-dependent pathway. Cytoskeleton rearrangement induced by lyso-Gb3 was normalized by the RIPK3 inhibitor. When mice were injected with lyso-Gb3, increased urine albuminuria, decreased podocyte counts in the glomeruli, and effaced foot processes were observed. Our results showed that lyso-Gb3 initiated albuminuria, a clinical manifestation of Fabry nephropathy, by podocyte loss and subsequent foot process effacement. These findings suggest a novel pathway in Fabry nephropathy.
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- 2021
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6. Synthesis and Photophysical Properties of a Series of Dimeric Indium Quinolinates
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Sang Woo Kwak, Ju Hyun Hong, Sang Hoon Lee, Min Kim, Yongseog Chung, Kang Mun Lee, Youngjo Kim, and Myung Hwan Park
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indium quinolinates ,charge transfer ,quantum yield ,radiative decay constant ,non-radiative constant ,Organic chemistry ,QD241-441 - Abstract
A novel class of quinolinol-based dimeric indium complexes (1–6) was synthesized and characterized using 1H and 13C(1H) NMR spectroscopy and elemental analysis. Compounds 1–6 exhibited typical low-energy absorption bands assignable to quinolinol-centered π–π* charge transfer (CT) transition. The emission spectra of 1–6 exhibited slight bathochromic shifts with increasing solvent polarity (p-xylene < tetrahydrofuran (THF) < dichloromethane (DCM)). The emission bands also showed a gradual redshift, with an increase in the electron-donating effect of substituents at the C5 position of the quinoline groups. The absolute emission quantum yields (ΦPL) of compounds 1 (11.2% in THF and 17.2% in film) and 4 (17.8% in THF and 36.2% in film) with methyl substituents at the C5 position of the quinoline moieties were higher than those of the indium complexes with other substituents.
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- 2020
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7. Role of the Nuclear Lamina in Age-Associated Nuclear Reorganization and Inflammation
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Lidya Kristiani, Miri Kim, and Youngjo Kim
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nuclear lamina ,lamins ,aging ,cellular senescence ,chronic inflammation ,3d chromatin structure ,hi-c ,Cytology ,QH573-671 - Abstract
Aging is characterized by the gradual loss of tissue function and integrity. Activation of inflammatory responses accelerates the deterioration of cells and tissues. Many studies have shown that alteration of the components of the nuclear lamina is associated with inflammation, both in vivo and in vitro. However, the mechanism by which the nuclear lamina regulates inflammation is largely unknown. Recent studies have suggested that the nuclear lamina regulates both organization of the three-dimensional chromatin structure at the nuclear periphery and global gene expression, such as the expression of inflammatory response genes. Here, we discuss the current updates in the research on nuclear lamina alteration, activation of inflammation, and nuclear reorganization in models of cellular senescence and organismal aging.
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- 2020
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8. Macrophage Lamin A/C Regulates Inflammation and the Development of Obesity-Induced Insulin Resistance
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Youngjo Kim, Princess Wendy Bayona, Miri Kim, Jiyeon Chang, Sunmin Hong, Yoona Park, Andrea Budiman, Yong-Jin Kim, Chang Yong Choi, Woo Seok Kim, Jongsoon Lee, and Kae Won Cho
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lamin A/C ,obesity ,inflammation ,insulin resistance ,macrophages ,adipose tissue ,Immunologic diseases. Allergy ,RC581-607 - Abstract
Obesity-induced chronic low-grade inflammation, in particular in adipose tissue, contributes to the development of insulin resistance and type 2 diabetes. However, the mechanism by which obesity induces adipose tissue inflammation has not been completely elucidated. Recent studies suggest that alteration of the nuclear lamina is associated with age-associated chronic inflammation in humans and fly. These findings led us to investigate whether the nuclear lamina regulates obesity-mediated chronic inflammation. In this study, we show that lamin A/C mediates inflammation in macrophages. The gene and protein expression levels of lamin A/C are significantly increased in epididymal adipose tissues from obese rodent models and omental fat from obese human subjects compared to their lean controls. Flow cytometry and gene expression analyses reveal that the protein and gene expression levels of lamin A/C are increased in adipose tissue macrophages (ATMs) by obesity. We further show that ectopic overexpression of lamin A/C in macrophages spontaneously activates NF-κB, and increases the gene expression levels of proinflammatory genes, such as Il6, Tnf, Ccl2, and Nos2. Conversely, deletion of lamin A/C in macrophages reduces LPS-induced expression of these proinflammatory genes. Importantly, we find that myeloid cell-specific lamin A/C deficiency ameliorates obesity-induced insulin resistance and adipose tissue inflammation. Thus, our data suggest that lamin A/C mediates the activation of ATM inflammation by regulating NF-κB, thereby contributing to the development of obesity-induced insulin resistance.
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- 2018
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9. Three Component Controls in Pillared Metal-Organic Frameworks for Catalytic Carbon Dioxide Fixation
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Jinmi Noh, Dasom Kim, Jihyun Lee, Minyoung Yoon, Myung Hwan Park, Kang Mun Lee, Youngjo Kim, and Min Kim
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metal-organic framework ,coordination polymer ,catalysis ,carbon dioxide ,cycloaddition ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Three components of pillared metal-organic frameworks (MOFs, three components = metal ion, carboxylic acid ligand, and N-chelating ligand) were controlled for CO2 cycloaddition catalysts to synthesize organic cyclic carbonates. Among the divalent metals, Zn2+ showed the best catalytic activity, and in DABCO (1,4-diazabicyclo[2.2.2]octane)-based MOFs, hydroxy-functionalized DMOF-OH was the most efficient MOF for CO2 cycloaddition. For the BPY (4,4’-bipyridyl)-type MOFs, all five prepared BMOFs (BPY MOFs) showed similar and good conversions for CO2 cycloaddition. Finally, this pillared MOF could be recycled up to three times without activity and crystallinity loss.
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- 2018
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10. Bis{2,2′-[methylazanediylbis(methylene)]bis(4,6-dimethylphenolato)-κ3O,N,O′}titanium(IV) toluene sesquisolvate
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Yongseog Chung and Youngjo Kim
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Crystallography ,QD901-999 - Abstract
The title compound, [Ti(C19H23NO2)2]·1.5C7H8, crystallizes with one titanium complex molecule per asymmetric unit together with one and a half toluene molecules. The TiIV atom is coordinated by two fully deprotonated O,N,O′-tridentate phenoxyamine ligands in a distorted octahedral environment. Within this arrangement the O atoms occupy the equatorial sites and the N atoms the axial sites. One of the toluene molecules is disordered over two sets of sites in a 0.628 (18):0.372 (18) ratio.
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- 2013
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11. 4-(1H-Tetrazol-5-yl)benzene-1,3-diol
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Youngjo Kim
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Crystallography ,QD901-999 - Abstract
In the title compound, C7H6N4O2, rings are almost coplanar, the dihedral angle between them being 8.45 (13)°. An intramolecular N—H...O hydrogen bond occurs. In the crystal, the molecules are linked by O—H...N and N—H...O hydrogen bonds into a three-dimensional network.
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- 2013
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12. 2-Benzhydryl-6-tert-butyl-4-methylphenol
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Sungwoo Yoon, Junseong Lee, and Youngjo Kim
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Crystallography ,QD901-999 - Abstract
The title compound, C24H26O, was prepared by the reaction between 2-tert-butyl-4-methylphenol and diphenylmethanol in the presence of sulfuric acid. Three benzene rings are attached directly to the central C—H group in a twisted propeller conformation with the local pseudo-C3 rotational axis coinciding with the C—H bond. There are three short C—H...O contacts in the molecule.
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- 2013
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13. 2,8,9-Tris(2-methylpropyl)-2,5,8,9-tetraaza-1λ5-phosphatricyclo[3.3.3.01,5]undecan-5-ium chloride dihydrate
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Junseong Lee and Youngjo Kim
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Crystallography ,QD901-999 - Abstract
The asymmetric unit of the title hydrated salt, C18H40N4P+·Cl−·2H2O, consists of two ionic molecules and four water molecules. The molecular geometry around the pentacoordinate P atom is trigonal–bipyramidal, with a H atom and an apical N atom in axial positions and three N atoms with isobutyl substituents in equatorial positions. The Cl− ions and water molecules are connected via O—H...Cl hydrogen bonds, forming chains along [100]. The ethylene bridging groups are disordered with refined site-occupancy ratios of 0.578 (9):0.422 (9).
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- 2012
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14. Bis(μ-trimethylsilanolato-κ2O:O)bis{[2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenolato-κ2N,O]zinc}
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Hwi Hyun Lee, Min Jeong Go, Ka Hyun Park, Youngjo Kim, and Junseong Lee
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Crystallography ,QD901-999 - Abstract
The binuclear title complex, [Zn2(C22H28N3O)2(C3H9OSi)2], has a crystallographic imposed centre of symmetry. The ZnII atom is coordinated by three O and one N atom from one 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenolate ligand and two bridging trimethylsilanolate anions in a distorted tetrahedral geometry. The dihedral angle between the benzotriazole ring system and the benzene ring is 19.83 (5)°. The tert-pentyl groups are disordered over two orientations with refined site-occupancy ratios of 0.858 (4):0.142 (4) and 0.665 (6):0.335 (6).
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- 2012
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15. μ-Oxido-bis[bis(pentafluorophenolato)(η5-pentamethylcyclopentadienyl)titanium(IV)]
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Junseong Lee and Youngjo Kim
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Crystallography ,QD901-999 - Abstract
The dinuclear title complex, [Ti2(C10H15)2(C6F5O)4O], features two TiIV atoms bridged by an O atom, which lies on an inversion centre. The TiIV atom is bonded to a η5-pentamethylcyclopentadienyl ring, two pentafluorophenolate anions and to the bridging O atom. The environment around the TiIV atom can be considered as a distorted tetrahedron. The cyclopentadienyl ring is disordered over two sets of sites [site occupancy = 0.824 (8) for the major component].
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- 2011
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16. Unification of an empirical and a physically-based approach to crystallization monitoring.
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Youngjo Kim, Kayla C. Dean, Yoshiaki Kawajiri, Ronald W. Rousseau, and Martha A. Grover
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- 2018
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17. Modeling of Nucleation, Growth, and Dissolution of Paracetamol in Ethanol Solution for Unseeded Batch Cooling Crystallization with Temperature-Cycling Strategy
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Youngjo Kim, Yoshiaki Kawajiri, Ronald W. Rousseau, and Martha A. Grover
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General Chemical Engineering ,General Chemistry ,Industrial and Manufacturing Engineering - Published
- 2023
18. Effect of bridging units on the photophysical properties of <scp> 4‐NEt 2 </scp> ‐appended salen−indium complexes
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Hanif Mubarok, Sang Woo Kwak, Ji Hye Lee, Hyonseok Hwang, Kang Mun Lee, Youngjo Kim, Min Hyung Lee, and Myung Hwan Park
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General Chemistry - Published
- 2022
19. A highly scalable and energy-efficient artificial neuron using an Ovonic Threshold Switch (OTS) featuring the spike-frequency adaptation and chaotic activity.
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Milim Lee, Youngjo Kim, Seong Won Cho, Joon Young Kwak, Hyunsu Ju, Yeonjin Yi, Byung-ki Cheong, and Suyoun Lee
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- 2018
20. Transformation of tert ‐Butyl Amide Directing Groups to Nitriles in Iridium‐Catalyzed C−H Bond Functionalizations
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Haneul Yoo, Hyun-Jin Kim, Min Kim, Kwangho Yoo, Dong-Wook Kim, Youngjo Kim, Myung Hwan Park, Dopil Kim, and Gary Jing Chuang
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Tert butyl ,Transformation (genetics) ,chemistry.chemical_compound ,C h bond ,Chemistry ,Amide ,Organic Chemistry ,chemistry.chemical_element ,Iridium ,Medicinal chemistry ,Catalysis - Published
- 2021
21. Sentence Difficulty Analysis with Local Feature Space and Global Distributional Difference.
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Young-Bum Kim, YoungJo Kim, and Yu-Seop Kim
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- 2012
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22. A Fast Intra Prediction Method Using the Distribution of Adjacent Pixels in HEVC.
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Youngjo Kim, Juwon Byun, and Jaeseok Kim
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- 2014
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23. A Pipelined Architecture for Intra PU Encoding in HEVC.
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Yunpyo Hong, Juwon Byun, Youngjo Kim, and Jaeseok Kim
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- 2014
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24. Synthesis and Photophysical Properties of ( <scp> Cl 2 Ph </scp> )Salen‐based Indium Complexes
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Myung Hwan Park, Won Hee Woo, Sang Woo Kwak, Youngjo Kim, Min Kim, Kang Mun Lee, and Seok Ho Lee
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chemistry.chemical_compound ,Materials science ,chemistry ,Luminophore ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Indium - Published
- 2020
25. Experimental, Structural, and Computational Investigation of Mixed Metal–Organic Frameworks from Regioisomeric Ligands for Porosity Control
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Min Kim, Younghu Son, Myung Hwan Park, Dopil Kim, Hyungjun Kim, Youngik Kim, Jiyoon Choi, Dong-Wook Kim, Hyeonbin Ha, Youngjo Kim, and Minyoung Yoon
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Materials science ,010405 organic chemistry ,Ligand ,Binding energy ,General Chemistry ,DABCO ,010402 general chemistry ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Adsorption ,chemistry ,General Materials Science ,Carboxylate ,Porosity ,Porous medium ,Octane - Abstract
Porosity control and structural analysis of metal–organic frameworks (MOFs) can be achieved using regioisomeric ligand mixtures. While ortho-dimethoxy-functionalized MOFs yielded highly porous structures and para-dimethoxy-functionalized MOFs displayed almost nonporous properties in their N2 isotherms after evacuation, regioisomeric ligand-mixed MOFs showed variable N2 uptake amount and surface area depending on the ligand-mixing ratio. The quantity of N2 absorbed was tuned between 20 and 300 cm3/g by adjusting the ligand-mixing ratio. Both experimental analysis and computational modeling were performed to understand the porosity differences between ortho- and para-dimethoxy-functionalized MOFs. Detailed structural analysis using X-ray crystallographic data revealed significant differences in the coordination environments of DMOF-[2,3-(OMe)2] and DMOF-[2,5-(OMe)2] (DMOF = dabco MOF, dabco = 1,4-diazabicyclo[2.2.0]octane). The coordination bond between Zn2+ and carboxylate in the ortho-functionalized DMOF-[2,3-(OMe)2] was more rigid than that in the para-functionalized DMOF-[2,5-(OMe)2]. Quantum-chemical simulation also showed differences in the coordination environments of Zn secondary building unit surrounded by methoxy-functionalized ligands and pillar ligands. In addition, the binding energy differences between Zn2+ and regioisomeric ligands (ortho- and para-dimethoxy-functionalized benzene-1,4-dicarboxylates) explained the rigidity and porosity changes of the mixed MOFs upon evacuation and perfectly matched with experimental N2 adsorption and X-ray crystallography data.
- Published
- 2020
26. Dual-Functional Electrolyte Additives toward Long-Cycling Lithium-Ion Batteries: Ecofriendly Designed Carbonate Derivatives
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Byeong Su Kim, Jung-Gu Han, Sang-Ho Lee, Koeun Kim, Youngjo Kim, Yoseph Kim, Deok-Ho Roh, Minsu Gu, Nam-Soon Choi, Sewon Park, Eunbyul Hwang, and Tae-Hyuk Kwon
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,Energy storage ,0104 chemical sciences ,law.invention ,Anode ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,law ,Degradation (geology) ,Carbonate ,General Materials Science ,Lithium ,0210 nano-technology ,Dissolution - Abstract
Long-term stability of the solid electrolyte interphase (SEI) and cathode-electrolyte interface (CEI) layers formed on anodes and cathodes is imperative to mitigate the interfacial degradation of electrodes and enhance the cycle life of lithium-ion batteries (LIBs). However, the SEI on the anode and CEI on the cathode are vulnerable to the reactive species of PF
- Published
- 2020
27. NaNO 3 ‐Promoted Mesoporous MgO for High‐Capacity CO 2 Capture from Simulated Flue Gas with Isothermal Regeneration
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Christopher W. Jones, Sang Jae Park, and Youngjo Kim
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Flue gas ,Sorbent ,Materials science ,General Chemical Engineering ,Induction period ,Sorption ,02 engineering and technology ,Partial pressure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Isothermal process ,0104 chemical sciences ,General Energy ,Chemical engineering ,Desorption ,Environmental Chemistry ,General Materials Science ,0210 nano-technology ,Inert gas - Abstract
NaNO3 -promoted MgO composite materials have been prepared and their ability to sorb CO2 at a concentration relevant to CO2 capture from flue gas is explored. The uptake kinetics and capacities of sorbents of different NaNO3 /MgO ratios are measured at intermediate temperatures of 230-300 °C. The sorbent with a NaNO3 /MgO ratio of 0.10 has the highest 12 h sorption capacity among sorbents with different NaNO3 loadings, and the highest sorption capacity of 11.2 mmol CO2 g-1 is observed at 260 °C. Intriguingly, an induction period is observed in the initial stage of CO2 sorption. In situ XRD analysis, in situ FTIR spectroscopy, and a comparison of the CO2 sorption behavior under simulated flue gas conditions in comparison to prior studies employing pure CO2 indicated that the sorption of CO2 occurred through nucleation of MgCO3 crystallites in the material. The data indicate that the concentration of CO2 within the molten medium of NaNO3 , which is affected by both the solubility of CO2 in molten NaNO3 and the partial pressure of CO2 in the surrounding atmosphere, has a critical impact on the length of the induction period. A partially desorbed sample after sorption of CO2 displays much-improved sorption kinetics in the next cycle and was able to sorb and desorb CO2 over multiple cycles at isothermal conditions by simply switching the feed gas from CO2 to inert gas.
- Published
- 2020
28. Optimal feedback control of batch self-assembly processes using dynamic programming
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Ronald W. Rousseau, Daniel J. Griffin, Youngjo Kim, Xun Tang, and Martha A. Grover
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0209 industrial biotechnology ,Computer science ,Dimensionality reduction ,Feedback control ,Supervised learning ,Control (management) ,Experimental data ,02 engineering and technology ,Industrial and Manufacturing Engineering ,Computer Science Applications ,Dynamic programming ,020901 industrial engineering & automation ,020401 chemical engineering ,Control and Systems Engineering ,Control theory ,Modeling and Simulation ,Simulated data ,State (computer science) ,0204 chemical engineering - Abstract
This paper reviews a previously-reported methodology for establishing feedback control of self-assembly. The methodology combines dimension reduction, supervised learning, and dynamic programming to obtain an optimal feedback control policy for reaching a desired assembled state. Sampled data are used in calculating the optimal feedback policy; this data can be generated using a predictive model (i.e. “simulated data”) or using experimental data. The control strategy is demonstrated, with both simulation and experimental results, for two applications: control of colloidal assembly (to produce perfect colloidal crystals) and control of crystallization from solution (to produce crystals of desired average size).
- Published
- 2020
29. Spirobifluorene‐Based o ‐Carboranyl Compounds: Insights into the Rotational Effect of Carborane Cages on Photoluminescence
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Junseong Lee, Hyonseok Hwang, Jiyeon Ryu, Kang Mun Lee, Seonah Kim, Ji Hye Lee, Hyunhee So, Myung Hwan Park, and Youngjo Kim
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Photoluminescence ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,General Chemistry ,Dihedral angle ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Crystallography ,Excited state ,Intramolecular force ,Carborane ,Absorption (chemistry) ,Luminescence ,Relative energy - Abstract
9,9'-Spirobifluorene-based closo-o-carboranyl (SFC1 and SFC2) compounds and their nido-derivatives (nido-SFC1 and nido-SFC2) were prepared and characterized. The two closo-compounds displayed major absorption bands assignable to π-π* transitions involving the spirobifluorene group, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene moieties. The nido-compounds exhibited slightly blueshifted absorption bands resulting from the absence of the ICT transitions corresponding to the o-carborane moieties due to the anionic character of the nido-o-carboranes. While SFC1 exhibited only high-energy emissions in THF at 298 K (only from locally excited (LE) states assignable to π-π* transitions on the spirobifluorene group), remarkable emissions in the low-energy region were observed in the rigid state such as in THF at 77 K and in the film state. SFC2 displayed intense emissions in the low-energy region in all states. The fact that neither of the nido-derivatives of SFC1 and SFC2 exhibited low-energy emissions and the TD-DFT calculation results of each closo-compound clearly verified that the low-energy emission was based on ICT-based radiative decay. The conformational barriers from each relative energy calculation upon changing the dihedral angles around the o-carborane cages for both compounds confirmed that the rotation of the o-carborane cages and terminal phenyl rings for SFC1 is freer than that for SFC2.
- Published
- 2019
30. Effect of the Metal within Regioisomeric Paddle‐Wheel‐Type Metal–Organic Frameworks
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Hyeonbin Ha, Youngik Kim, Yoodae Song, Jihyun Lee, Minyoung Yoon, Dopil Kim, Min Kim, Suyeon Kim, Myung Hwan Park, Hyungjun Kim, and Youngjo Kim
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010405 organic chemistry ,Organic Chemistry ,Regioselectivity ,General Chemistry ,DABCO ,engineering.material ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,Type metal ,Paddle wheel ,Adsorption ,chemistry ,visual_art ,engineering ,visual_art.visual_art_medium ,Physical chemistry ,Metal-organic framework ,Octane - Abstract
The effect of metal on the degree of flexibility upon evacuation of metal-organic frameworks (MOFs) has been revealed with positional control of the organic functionalities. Although Co-, Cu-, and Zn-based DMOFs (DMOF = DABCO MOF, DABCO = 1,4-diazabicyclo[2.2.2]octane) with ortho-ligands (2,3-NH2 Cl) have frameworks that are inflexible upon evacuation, MOFs with para-ligands (2,5-NH2 Cl) showed different N2 uptake amounts after evacuation by metal exchange. Considering that the structural analyses were not fully sufficiently different to explain the drastic changes in N2 adsorption after evacuation, quantum chemical simulation was explored. A new index (η) was defined to quantify the regularity around the metal based on differences in the oxygen-metal-oxygen angles. Within 2,5-NH2 Cl, the η value becomes larger as the metal are varied from Co to Zn. A large η value means that the structures around the metal center are less ordered. These results can be used to explain flexibility changes upon evacuation by altering the metal cation in this regioisomeric system.
- Published
- 2019
31. Efficient Aluminum Catalysts for the Chemical Conversion of CO 2 into Cyclic Carbonates at Room Temperature and Atmospheric CO 2 Pressure
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Myung Hwan Park, Youngjo Kim, Duseong Ahn, Ran Kim, Kyunglim Hyun, and Yoseph Kim
- Subjects
General Chemical Engineering ,Heteroatom ,Epoxide ,Homogeneous catalysis ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Medicinal chemistry ,Cycloaddition ,0104 chemical sciences ,Turnover number ,Catalysis ,chemistry.chemical_compound ,General Energy ,chemistry ,Electronic effect ,Environmental Chemistry ,General Materials Science ,0210 nano-technology ,Pendant group - Abstract
A series of dimeric aluminum compounds [Al(OCMe2 CH2 N(R)CH2 X)]2 [X=pyridin-2-yl, R=H (PyrH ); X= pyridin-2-yl, R=Me (PyrMe ); X=furan-2-yl, R=H (FurH ); X= furan-2-yl, R=Me (FurMe ); X=thiophen-2-yl, R=H (ThioH ); X= thiophen-2-yl, R=Me (ThioMe )] containing heterocyclic pendant group attached to the nitrogen catalyze the coupling of CO2 with epoxides under ambient conditions. In a comparison of their catalytic activities with those of aluminum complexes without pendant groups at N [X=H, R=H (HH ); X=H, R=Me (HMe )] or with non-heterocyclic pendant groups [X=CH2 CH2 OMe, R=H (OMeH ); X=CH2 CH2 NMe2 , R=H (NMe2H ); X=CH2 CH2 NMe2 , R=Me (NMe2Me )], complexes containing heterocycles, in conjunction with (nBu)4 NBr as a cocatalyst, show higher catalytic activities for the synthesis of cyclic carbonates under the same ambient conditions. The best catalyst system for this reaction is PyrH /(nBu)4 NBr system, which gives a turnover number of 99 and a turnover frequency of 4.1 h-1 , making it 14- and 20-times more effective than HH /(nBu)4 NBr and HMe /(nBu)4 NBr, respectively. Although there are no direct interactions between the aluminum and the heteroatoms in the heterocyclic pendants, electronic effects combined with the increased local concentration of CO2 around the active centers influences the catalytic activity in the coupling of CO2 with epoxides. In addition, PyrH /(nBu)4 NBr shows broad epoxide substrate scope and seven terminal epoxides and two internal epoxides undergo the designed reaction.
- Published
- 2019
32. A Series of Quinolinol-Based Indium Luminophores: A Rational Design Approach for Manipulating Photophysical Properties
- Author
-
Sang Woo Kwak, Yongseog Chung, Ji Hye Lee, Youngjo Kim, Junseong Lee, Joong Chul Choe, Heuiseok Shin, Hyonseok Hwang, Min Kim, Myung Hwan Park, Moon Bae Kim, Ji Yeon Ryu, and Kang Mun Lee
- Subjects
010405 organic chemistry ,Ligand ,Rational design ,Quantum yield ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Quinolinate ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Structural stability ,Physical chemistry ,Quantum efficiency ,Physical and Theoretical Chemistry ,Methyl methacrylate ,Indium - Abstract
An approach to the design of a series of quinolinol-based indium complexes that can exhibit different optical properties is proposed. Mono-incorporated (Inq1 and InMeq1), bis-incorporated (InMeq2), and tris-incorporated (Inq3 and InMeq3) indium quinolinate complexes have been prepared. These complexes have also been characterized by X-ray crystallography. The photophysical properties of these complexes have also been examined by a combination of experimental and theoretical techniques. The indium complexes with a single quinolinol ligand (Inq1 and InMeq1) showed higher quantum efficiency than those with two or three quinolinate ligands; in particular, InMeq1 exhibited the highest quantum yield [ΦPL = 59% in poly(methyl methacrylate) film]. The insights into the nature of these findings were obtained by the sequential synthesis of the quinolinol-based indium luminophores and a detailed investigation of their structural stability.
- Published
- 2019
33. Systematic Control of the Overlapping Energy Region for an Efficient Intramolecular Energy Transfer: Functionalized Salen–Al/Triphenylamine Guest–Host Assemblies
- Author
-
Hyonseok Hwang, Sang Woo Kwak, Ji Hye Lee, Kang Mun Lee, Min Kim, Myung Hwan Park, Hyomin Jin, Yongseog Chung, and Youngjo Kim
- Subjects
010405 organic chemistry ,Ethylenediamine ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,Triphenylamine ,01 natural sciences ,Transition state ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Intramolecular force ,Moiety ,Density functional theory ,Physical and Theoretical Chemistry ,Tetrahydrofuran - Abstract
A series of triphenylamine (TPA)-containing salen-Al assembly dyads, [salen(3- tBu-5-R)2Al(OC6H4- p-N(C6H5)2)] [salen = N, N'-bis(salicylidene)ethylenediamine; R = H (D1), tBu (D2), Ph (D3), OMe (D4), and NMe2 (D5)], were prepared in good yield (50-80%) and fully characterized by NMR spectroscopy and elemental analysis. Both the UV/vis absorption and photoluminescence (PL) spectra of D1-D4, except for D5, in a tetrahydrofuran solution exhibited dual patterns, which are assignable to the salen-Al-centered π-π* transition (low-energy region) and the TPA-centered π-π* transition (high-energy region). In particular, the emission spectra of the dyads displayed interesting dual-emissive patterns via a significant intramolecular energy transfer (IET) process between the salen-Al moiety and TPA group. Notably, this IET process was systematically tuned by varying the substituents and dominantly observed in the rigid state. More interestingly, compared to the salen-Al complexes (A1-A4) without the TPA group, D1-D4 exhibited enhanced quantum efficiencies. Time-dependent density functional theory calculations on the S1-optimized structures of D1-D5 further supported these experimental results by indicating the existence of independent transition states between the salen-Al moiety and TPA group in the assembly dyads. The present study reports the first example of salen-Al complexes bearing electron-rich TPA moieties.
- Published
- 2019
34. Europium‐Catalyzed Aerobic Oxidation of Alcohols to Aldehydes/Ketones and Photoluminescence Tracking
- Author
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Kang Mun Lee, Youngjo Kim, Min Kim, Youngik Kim, Seongwoo Kim, Myung Hwan Park, and Hyomin Jin
- Subjects
Photoluminescence ,chemistry ,Alcohol oxidation ,Redox cycle ,chemistry.chemical_element ,Homogeneous catalysis ,General Chemistry ,Europium ,Photochemistry ,Catalysis - Published
- 2019
35. Role of lamins in 3D genome organization and global gene expression
- Author
-
Yixian Zheng, Xiaobin Zheng, and Youngjo Kim
- Subjects
lcsh:QH426-470 ,Genomics ,lads ,tads ,Chromosome conformation capture ,03 medical and health sciences ,Gene expression ,Animals ,Humans ,lamin ,lcsh:QH573-671 ,030304 developmental biology ,Genomic organization ,Cell Nucleus ,0303 health sciences ,Genome ,hi-c ,biology ,lcsh:Cytology ,Extra View ,3d genome ,030302 biochemistry & molecular biology ,Cell Biology ,Lamins ,Chromatin ,Cell biology ,lcsh:Genetics ,Histone ,Gene Expression Regulation ,biology.protein ,Nuclear lamina ,hilands ,Lamin ,nuclear lamina - Abstract
Genome-wide mapping of lamin-B1-genome interactions has shown that gene-poor and transcriptionally inactive genomic regions are associated with the nuclear lamina. Numerous studies have suggested that lamins, the major structural components of the nuclear lamina, play a role in global chromatin organization and gene expression. How lamins could influence the 3D genome organization and transcription from the nuclear periphery has, however, remained unclear. Our recent studies showed that lamins differentially regulate distinct lamina-associated chromatin domains (LADs) at the nuclear periphery, which can in turn influence global 3D genome organization and gene expression. In this Extra View, we discuss how by using various genomics tools, it has become possible to reveal the functions of lamins in orchestrating 3D genome organization and gene expression. Abbreviations: 3D: three dimensional; LAD: lamina-associated chromatin domain; 3C: Chromosome Conformation Capture; TAD: topologically associated domain; HiLands: Histone and lamina landscape; NL: nuclear lamina; mESC: mouse embryonic stem cell; DamID: DNA adenine methyltransferase identification
- Published
- 2019
36. Synthesis of o-carborane-functionalized metal–organic frameworks through ligand exchanges for aggregation-induced emission in the solid state
- Author
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Kang Mun Lee, Minyoung Yoon, Youngjo Kim, Jihyun Lee, Sangdon Choi, Min Kim, Jooyeon Lee, Myung Hwan Park, Chan Hee Ryu, and Ha-Eun Lee
- Subjects
General method ,Photoluminescence ,010405 organic chemistry ,Ligand ,Chemistry ,Metals and Alloys ,Solid-state ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Materials Chemistry ,Ceramics and Composites ,Carborane ,Metal-organic framework ,Aggregation-induced emission - Abstract
The carborane (CB)-functionalized ligand was installed in a variety of MOFs through postsynthetic ligand exchange processes. This methodology is a general method for preparing o-CB-functionalized MOFs with known frameworks. Furthermore, the photoluminescence (PL) spectra revealed intriguing aggregation-induced emission (AIE) features following the systematic incorporation of o-CB functionalities into framework-type materials.
- Published
- 2019
37. Genetic activation of parkin rescues TAF15-induced neurotoxicity in a Drosophila model of amyotrophic lateral sclerosis
- Author
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Seongsoo Lee, Yu-Mi Jeon, Sanghyun Lee, Mihye Lee, Youngjo Kim, Hyungjun Kim, Kiyoung Kim, Hyun-Jun Choi, Hayoung Kim, and Sun Joo Cha
- Subjects
Transcriptional Activation ,0301 basic medicine ,Cytoplasm ,Aging ,Ubiquitin-Protein Ligases ,Gene Expression ,Neuroprotection ,Parkin ,03 medical and health sciences ,0302 clinical medicine ,Ubiquitin ,medicine ,Animals ,Drosophila Proteins ,Amyotrophic lateral sclerosis ,TAF15 ,Neurons ,TATA-Binding Protein Associated Factors ,biology ,General Neuroscience ,Amyotrophic Lateral Sclerosis ,Neurodegeneration ,Neurotoxicity ,medicine.disease ,nervous system diseases ,Ubiquitin ligase ,Cell biology ,Disease Models, Animal ,030104 developmental biology ,biology.protein ,Drosophila ,Neurology (clinical) ,Geriatrics and Gerontology ,030217 neurology & neurosurgery ,Protein Binding ,Developmental Biology - Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that is characterized pathologically by the loss of motor neurons. Mutations in the TAF15 gene have been implicated in the pathogenesis of ALS. TATA-binding protein associated factor 15 (TAF15) accumulates as cytoplasmic aggregates in neuronal cells, the clearance of which may be a therapeutic strategy for ALS. However, the identification of a novel regulator for protection against a TAF15-induced proteinopathy and the exact pathogenic mechanism of TAF15-induced neurodegeneration remain to be elucidated. Here, we show that parkin directly binds to TAF15 and that parkin overexpression can suppress the defective phenotypes, including the life span and locomotive activity of a TAF15-induced proteinopathy. We also found that overexpression of parkin in neuronal cells leads to a reduction in TAF15 levels, because of the E3 ubiquitin ligase activity of parkin. Our study provides in vivo evidence supporting the use of parkin for neuroprotection in a TAF15-induced proteinopathy and offers new insights into the pathogenic mechanisms underlying TAF15-induced ALS.
- Published
- 2019
38. Systematic design of indium-based luminophores with color-tunable emission via combined manipulation of HOMO and LUMO levels
- Author
-
Youngjo Kim, Hyonseok Hwang, Hyomin Jin, Kang Mun Lee, Won Hee Woo, Min Kim, Ji Hye Lee, Heuiseok Shin, Kyunglim Hyun, and Myung Hwan Park
- Subjects
010405 organic chemistry ,Process Chemistry and Technology ,General Chemical Engineering ,Aryl ,Substituent ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,chemistry ,Intramolecular force ,Bathochromic shift ,Emission spectrum ,HOMO/LUMO ,Indium - Abstract
A series of indium complexes with salen ligands bridged by aryl groups such as [Ar-{N CH(C6H2-3-tBu-5-R)}2]In-Me (Ar = 4,5-dimethyl-1,2-phenylene, 1,2-phenylene, and 3,4-naphthylene; R = H, Br, tBu, Me, OMe, NMe2, and NMe3+) were prepared and fully identified by NMR spectroscopy and elemental analysis. All indium complexes are highly stable in air and aqueous solutions. Among these complexes, the structurally characterized complexes [(4,5-dimethylphenylene)bis(3-tert-butyl-5-methylsalicylideneiminato)-κN,N′,O,O']methylindium(III) and [(2,3-naphthanlene)bis(3-tert-butyl-5-methylsalicylideneiminato)-κN,N′,O,O']methylindium(III) have slightly distorted square-pyramidal geometries around the central indium atoms. The UV/Vis absorption and emission spectra of all indium complexes exhibited significant intramolecular charge transfer (ICT) transitions assigned to the aryl salen-centered π-π* transitions, which displayed a gradual bathochromic shift, resulting from the electronic alteration of the substituent at the C5 position of phenoxy ring. Furthermore, the emission bands also gradually red-shifted as the electron-donating effect of bridging aryl groups decreased. In particular, the emission spectra of the indium complexes were observed in the visible region ranging from green (ca. 500 nm) to deep red (ca. 700 nm). The colors were obtained by manipulating the HOMO and LUMO energy levels, which was further supported by both electrochemical data and theoretical calculations.
- Published
- 2018
39. RIPK3 Contributes to Lyso-Gb3-Induced Podocyte Death
- Author
-
Youngjo Kim, Jong-Seok Moon, Eun Young Lee, Eun Soo Lee, Choon Hee Chung, Miri Kim, Ji-Hye Lee, Jeong Suk Kang, So-Young Kim, Seong-Woo Lee, and Samel Park
- Subjects
0301 basic medicine ,Necroptosis ,030232 urology & nephrology ,necroptosis ,medicine.disease_cause ,lyso-Gb3 ,RIPK3 ,Models, Biological ,Article ,Podocyte ,Nephropathy ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Lysosomal storage disease ,Animals ,lcsh:QH301-705.5 ,Cytoskeleton ,alpha-galactosidase A ,Sphingolipids ,Kidney ,Fabry disease ,Cell Death ,Podocytes ,business.industry ,General Medicine ,medicine.disease ,Mice, Inbred C57BL ,030104 developmental biology ,medicine.anatomical_structure ,lcsh:Biology (General) ,Receptor-Interacting Protein Serine-Threonine Kinases ,alpha-galactosidase ,Albuminuria ,Cancer research ,Female ,Glycolipids ,medicine.symptom ,Reactive Oxygen Species ,business ,Injections, Intraperitoneal ,Oxidative stress - Abstract
Fabry disease is a lysosomal storage disease with an X-linked heritage caused by absent or decreased activity of lysosomal enzymes named alpha-galactosidase A (&alpha, gal A). Among the various manifestations of Fabry disease, Fabry nephropathy significantly affects patients&rsquo, morbidity and mortality. The cellular mechanisms of kidney damage have not been elusively described. Necroptosis is one of the programmed necrotic cell death pathways and is known to play many important roles in kidney injury. We investigated whether RIPK3, a protein phosphokinase with an important role in necroptosis, played a crucial role in the pathogenesis of Fabry nephropathy both in vitro and in vivo. The cell viability of podocytes decreased after lyso-Gb3 treatment in a dose-dependent manner, with increasing RIPK3 expression. Increased reactive oxygen species (ROS) generation after lyso-Gb3 treatment, which was alleviated by GSK&rsquo, 872 (a RIPK3 inhibitor), suggested a role of oxidative stress via a RIPK3-dependent pathway. Cytoskeleton rearrangement induced by lyso-Gb3 was normalized by the RIPK3 inhibitor. When mice were injected with lyso-Gb3, increased urine albuminuria, decreased podocyte counts in the glomeruli, and effaced foot processes were observed. Our results showed that lyso-Gb3 initiated albuminuria, a clinical manifestation of Fabry nephropathy, by podocyte loss and subsequent foot process effacement. These findings suggest a novel pathway in Fabry nephropathy.
- Published
- 2021
40. Separation of <scp> C 2 –C 4 </scp> hydrocarbons from methane by zeolite <scp>MFI</scp> hollow fiber membranes fabricated from <scp>2D</scp> nanosheets
- Author
-
Akshay Korde, Shaowei Yang, Sankar Nair, Christopher W. Jones, Youngjo Kim, and Byunghyun Min
- Subjects
chemistry.chemical_compound ,Environmental Engineering ,Membrane ,Materials science ,chemistry ,Chemical engineering ,General Chemical Engineering ,Fiber ,Zeolite ,Methane ,Biotechnology - Published
- 2020
41. Separation of C2-C4 Hydrocarbons from Methane by Zeolite MFI Hollow Fiber Membranes Fabricated from 2D Nanosheets
- Author
-
Byunghyun Min, Akshay Korde, Shaowei Yang, Youngjo Kim, Christopher Jones, and Sankar Nair
- Published
- 2020
42. Ir-Catalyzed C-H Amidation Using Carbamoyl Azides for the Syntheses of Unsymmetrical Ureas
- Author
-
Jooyeon Lee, Kwangho Yoo, Min Kim, Youngjo Kim, Hyun-Jin Kim, and Myung Hwan Park
- Subjects
Azides ,010405 organic chemistry ,Nitrogen ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,Iridium ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Urea ,Nitrogen source - Abstract
An iridium-catalyzed C–H amidation for the syntheses of unsymmetrical urea was developed using carbamoyl azides (R(R′)N–C(O)-N3) as the nitrogen source. A combination of iridium and silver gave an ...
- Published
- 2020
43. NaNO
- Author
-
Sang Jae, Park, Youngjo, Kim, and Christopher W, Jones
- Abstract
NaNO
- Published
- 2020
44. Biological Fixed Film
- Author
-
Eun-Sik, Kim, Youngjo, Kim, Yongeun, Park, and Jeongdong, Choi
- Subjects
Bioreactors ,Biofilms ,Ecological Modeling ,Electrochemistry ,Quorum Sensing ,Environmental Chemistry ,Wastewater ,Waste Disposal, Fluid ,Waste Management and Disposal ,Pollution ,Water Science and Technology - Abstract
The review includes scientific literatures published in the year of 2017 regarding the uses of biofilm and bioreactor to treat wastewater. Topics considered are: biofilm formation and factors that impact biofilm formation; extracellular polymeric substance from biofilms; biofilm consortia and quorum sensing; biofilm associated phage; biofilm reactors; and biofilm in bioelectrochemical systems.
- Published
- 2018
45. Functional group effects on a metal-organic framework catalyst for CO2 cycloaddition
- Author
-
Jihyun Lee, Min Kim, Youngjo Kim, Minyoung Yoon, Myung Hwan Park, Jinmi Noh, Hyojin Park, and Youngik Kim
- Subjects
Chemistry ,General Chemical Engineering ,Carbon fixation ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cycloaddition ,0104 chemical sciences ,Catalysis ,Metal ,chemistry.chemical_compound ,visual_art ,Functional group ,visual_art.visual_art_medium ,Organic chemistry ,Reactivity (chemistry) ,0210 nano-technology ,Porosity - Abstract
A variety of metal-organic frameworks (MOFs) have been reported as efficient catalysts for CO2 fixation reactions, such as cycloaddition to cyclic carbonates. The permanent porosity of the frameworks and the Lewis acidity of the MOF metal sites have been considered as the major contributors to the catalytic activity in the cycloaddition of CO2. In this study, we have, instead, focused on the effects of the organic functional groups for effective catalytic ability. A total of eight different functionalized Zr-based MOFs were tested. It was revealed that the non-functionalized pristine UiO-66 MOF (UiO = University of Oslo) showed the best conversion at low temperature (77% at 50 °C), whereas the hydroxy-functionalized UiO-66-OH MOF displayed the best conversion at high temperature (91% at 140 °C). The Zr-MOF could be recycled up to four times without a significant decrease in the reactivity.
- Published
- 2018
46. Scorpionate Catalysts for Coupling CO2 and Epoxides to Cyclic Carbonates: A Rational Design Approach for Organocatalysts
- Author
-
Yoseph Kim, Youngjo Kim, Mannkyu Hong, Mu-Hyun Baik, Hee Jin Cho, and Hyejin Kim
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Hydrogen bond ,Organic Chemistry ,Iodide ,Rational design ,Epoxide ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Nucleophile ,Intramolecular force ,Yield (chemistry) - Abstract
Novel scorpionate-type organocatalysts capable of effectively coupling carbon dioxide and epoxides under mild conditions to afford cyclic propylene carbonates were developed. On the basis of a combined experimental and computational study, a precise mechanistic proposal was developed and rational optimization strategies were identified. The epoxide ring-opening, which requires an iodide as a nucleophile, was enhanced by utilizing an immonium functionality that can form an ion pair with iodide, making the ring-opening process intramolecular. The CO2 activation and cyclic carbonate formation were catalyzed by the concerted action of two hydrogen bonds originating from two phenolic groups placed at the claw positions of the scorpionate scaffold. Electronic tuning of the hydrogen bond donors allowed to identify a new catalyst that can deliver >90% yield for a variety of epoxide substrates within 7 h at room temperature under a CO2 pressure of only 10 bar, and is highly recyclable.
- Published
- 2018
47. Epitaxial Ge Solar Cells Directly Grown on Si (001) by MOCVD Using Isobutylgermane
- Author
-
Jaejin Lee, Kangho Kim, Won-Kyu Park, Chang Zoo Kim, Youngjo Kim, and Ho Kwan Kang
- Subjects
010302 applied physics ,Materials science ,business.industry ,Energy conversion efficiency ,General Physics and Astronomy ,Isobutylgermane ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Transmission electron microscopy ,0103 physical sciences ,Solar cell ,Optoelectronics ,Metalorganic vapour phase epitaxy ,Dislocation ,0210 nano-technology ,business - Abstract
Epitaxial Ge layers have been grown on Si (001) substrates by metalorganic chemical vapor deposition (MOCVD) using an isobutylgermane (IBuGe) metalorganic source. Low and high temperature two-step growth and post annealing techniques are employed to overcome the lattice mismatch problem between Ge and Si. It is demonstrated that high quality Ge epitaxial layers can be grown on Si (001) by using IBuGe with surface RMS roughness of 2 nm and an estimated threading dislocation density of 4.9 × 107 cm −2. Furthermore, single-junction Ge solar cells have been directly grown on Si substrates with an in situ MOCVD growth. The epitaxial Ge p-n junction structures are investigated with transmission electron microscopy and electrochemical C-V measurements. As a result, a power conversion efficiency of 1.69% was achieved for the Ge solar cell directly grown on Si substrate under AM1.5G condition.
- Published
- 2018
48. Titanium complexes containing tridentate [ONO] type Schiff base ligands for the cycloaddition reaction of CO2 to propylene oxide
- Author
-
Youngjo Kim, Min Jeong Go, Ji Yeon Ryu, Young Min Byun, Ji Min Lee, Kyung Su Na, and Junseong Lee
- Subjects
Schiff base ,010405 organic chemistry ,Chemistry ,Ligand ,chemistry.chemical_element ,010402 general chemistry ,Condensation reaction ,01 natural sciences ,Cycloaddition ,0104 chemical sciences ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Polymer chemistry ,Materials Chemistry ,Propylene oxide ,Physical and Theoretical Chemistry ,Chirality (chemistry) ,Titanium - Abstract
New titanium complexes, TiLCl2(THF) and TiL2, containing the tridentate chiral Schiff-base ligand, L, prepared from the condensation reaction of 2,4-pentadione and (1R,2S)-(−)-1-aminoindanol, were synthesized and characterized by various analytical methods including X-ray crystallography. Ligand L acted as a dianionic tridentate ligand and, owing to a chiral center in the aminoindanol part, imparted chirality to its titanium complexes. The newly synthesized titanium complexes and previously reported analogous Ti complexes were used as catalysts in the cycloaddition of CO2 to propylene oxide as the first representatives of titanium complexes with tridentate Schiff base ligands to have been used for this purpose. These complexes provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activities with TOF values up to 131 h−1 in comparison with the previously reported catalyst systems.
- Published
- 2018
49. Defect Engineering into Metal–Organic Frameworks for the Rapid and Sequential Installation of Functionalities
- Author
-
Seongwoo Kim, Youngjo Kim, Min Kim, Hyojin Park, Myung Hwan Park, and Byung Hyuck Jung
- Subjects
010405 organic chemistry ,Chemistry ,Ligand ,fungi ,Defect engineering ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,0104 chemical sciences ,Inorganic Chemistry ,Time frame ,Surface modification ,Metal-organic framework ,Physical and Theoretical Chemistry - Abstract
Postsynthetic treatments are well-known and important functionalization tools of metal-organic frameworks (MOFs). Herein, we have developed a practical and rapid postsynthetic ligand exchange (PSE) strategy using a defect-controlled MOF. An increase in the number of defects amounts to MOFs with enhanced rates of ligand exchange in a shorter time frame. An almost quantitative exchange was achieved by using the most defective MOFs. This PSE strategy is a straightforward method to introduce a functionality into MOFs including bulky or catalytically relevant moieties. Furthermore, some mechanistic insights into PSE were revealed, allowing for a sequential ligand exchange and the development of multifunctional MOFs with controlled ligand ratios.
- Published
- 2018
50. A salen–Al/carbazole dyad-based guest–host assembly: enhancement of luminescence efficiency via intramolecular energy transfer
- Author
-
Junseong Lee, Youngjo Kim, Hyonseok Hwang, Kang Mun Lee, Heuiseok Shin, Myung Hwan Park, Sang Woo Kwak, Min Kim, Yongseog Chung, Hyomin Jin, and Ji Hye Lee
- Subjects
Materials science ,Guest host ,010405 organic chemistry ,Carbazole ,Energy transfer ,Enhanced luminescence ,Metals and Alloys ,General Chemistry ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Materials Chemistry ,Ceramics and Composites ,Moiety ,Emission spectrum ,Luminescence - Abstract
A novel class of salen-Al/carbazole dyads (D1 and D2) was synthesized and fully identified. The emission spectra of the dyads presented intriguing dual-emission patterns via an intramolecular energy transfer (IET) state in solution. Furthermore, the IET feature of the dyads was clearly observed in the rigid state. Interestingly, the emission efficiency of the dyads was enhanced by the significant IET process from the carbazole group to the salen-Al moiety. Particularly, D1 exhibited a nearly three-fold enhanced luminescence efficiency compared to the corresponding mononuclear aluminum complexes (A1). Such an emission process of these guest-host systems was further supported by theoretical calculation.
- Published
- 2018
Catalog
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